B.: VÉASE TAMBIÉN EL SUBARTÍCULO 3A201.b

Linnaeus’ Sexual System was popular largely because of its simplicity. In fact it did not classify plants in quite the most slavishly simple manner that could be envisaged (i.e. only on the number of stamens and pistils), because the classes 14-23 were based on somewhat more subtle characters than stamen number alone. Hence Digitalis, the foxglove, which has four stamens, appeared not in the Tetrandria, but in Didynamia, with two long and two short stamens. Thus there is slightly less discrepancy between the groups of the Sexual System and those of modern systems than would otherwise have been the case. Nevertheless, the Sexual System was very artificial. Linnaeus

himself was fully aware of this, and sought at various times to present the rudiments of a natural system based on overall similarities, as had Ray and others before him. In 1738 he formulated an outline of a possible system and in 1764 he listed 58 ‘natural orders’ in an appendix to the sixth edition of

Genera Plantarum. These ‘natural orders’ are what we today call families, and

many of them corresponded closely with modern families.

The foundation of the modern families comes mainly, however, from the work of French taxonomists in the latter part of the eighteenth century, notably M. Adanson (1727-1806), A.-L.de Jussieu (1748-1836) and J. de Lamarck (1744-1829), who never followed the Sexual System.

Adanson produced his Families des Plantes in 1763. Today he is most remembered for championing the idea that in classification one should use a great range of characters covering all aspects of the plant, and without placing greater emphasis on some than on others. This is called an empirical approach. He was a severe critic of Linnaeus’ works, and considered Tournefort’s classification, upon which he improved, far superior. Adanson recognized 58 families of plants, many of them with the same circumscription as today.

A.-L. de Jussieu was a student of his uncle, B. de Jussieu, as was Adanson. In his most significant work, Genera Plantarum (1789), he divided plants into three groups: Acotyledons (cryptogams plus a few misunderstood monocoty­ ledons); Monocotyledones (monocotyledons); and Dicotyledones (dicotyle­ dons and gymnosperms). Within the last two groups he used many of the familiar modern characters (superior versus inferior ovaries, stamens free versus attached to corolla, fused versus free petals, etc.), so that plants as a whole were divided into 15 classes and 100 natural orders (families). Although several of these were very artificial, a good proportion are still found similarly delimited in modern classifications, and de Jussieu’s Genera can be regarded as the immediate progenitor of the modern system.

Lamarck is best known for his theory of evolution, Lamarckism, whereby characters acquired during life become inherited. This theory was, however, finalized after his main taxonomic contributions appeared. These comprised his Flore Frangoise (1778, with later editions) and the botanical part of Panckoucke’s Encyclopedic Methodique (1783-1798, completed by J. L. M. Poiret, 1804—1817). Lamarck’s taxonomic fame rests not on his system of classification (the Encyclopedie, while arranged alphabetically, advocated the de Jussieu system) but upon his realization that a natural system of classifica­ tion was not the best for rapid identification. Accordingly, his Flore Frangoise contained an analytical method, closely similar to the dichotomous keys of modern Floras, which was meant to be simply a method of identification.

The work epitomized by these three Frenchmen, plus progress in ah understanding of plant anatomy and physiology, the greatly increased ex­ ploration of the tropics and southern hemisphere and the cultivation in European gardens of many of the plants brought back, and the development and widespread use of better optical aids, paved the way for the nineteenth century taxonomists.

Before the nineteenth century knowledge of plant structure was confined to exomorphic aspects and to a very elementary outline of endomorphic features, which had been established by the seventeenth century anatomists

such as N. Grew and M. Malpighi in their works of the 1670s. R. J. Camerarius had in 1694 experimentally demonstrated the male and female nature of the stamens and carpels, and T. Fairchild in 1717 had produced what was probably the first experimental interspecific hybrid (between a Carnation and a Sweet William, two species of Dianthus). Nevertheless, little detail of sex in plants was grasped, and hence the true (and widely divergent) nature of cryptogams was unknown. In the nineteenth century these topics received a great deal more attention in various countries of Europe. The names of three men should be mentioned: R. Brown, who in the early part of the century investigated the detailed floral morphology of many groups, recognized the naked ovule of the gymnosperms, and discovered the nature of the cell nucleus; W. Hofmeister, who in the mid part of the century worked out details of the life cycle of many cryptogamic groups, especially bryophytes and pteridophytes; and E. Strasburger, who later in the century carried further Hofmeister’s work and was the first to observe sexual fusion in higher plants.

Exploration of Asia, Africa and America was providing an enormous number of new species. This can be illustrated by reference to the works of F. H. A. Humboldt, A. J. A. Bonpland and C. S. Kunth on the South Amer­ ican tropics. Of their many impressive works, Nova Genera et Species

Plantarum (1816-1825) in 7 volumes and 36 parts is the greatest, and it led to

the production, started by C. F. P. von Martius, of Flora Brasiliensis (1840- 1906). They had carried forward a thirst for scientific exploration so well exhibited by James Cook and the natural historians who accompanied him on his three great voyages (1768-1780). Classifications which appeared during the nineteenth century were therefore devised in a lively and dynamic environment, and not surprisingly there were many of them.

A. P. de Candolle (1778-1841), a Swiss botanist, contributed much to the development of higher plant classification, as well as to other fields of plant science. His book Theorie Elementaire de la Botanique (1813), in which he first introduced the word taxonomy, set out an outline classification of plants as well as the principles which he thought should govern classification; a good account of these is given by Cain.58 He divided plants into two major groups: Cellulares and Vasculares, the non-vascular and vascular plants respectively. His most important work was Prodromus Systematis Naturalis Regni Vegeta-

bilis (1823-1873), a 17-volume book written by 35 authors under the general

editorship of A. P. de Candolle (Vols. 1-7) and, after the latter’s death, by his son, A. de Candolle (1806-1893). This covered all species of dicotyledons in the world, accounting for over 58 000 species in 161 families (Fig. 2.5). Included in these were gymnosperms, still placed close to the catkin-bearing dicotyledons, but the work remained unfinished in that the monocotyledons and cryptogams were never covered. This mammoth undertaking represents the most modern world monograph of dicotyledons, and for many individual families no later ones have since appeared. De Candolle also published a great number of family and genus monographs, most of them dating from before his Prodromus. De Candolle’s system was an improvement upon that of de Jussieu, and in many general respects it resembles many twentieth century schemes.

Most other nineteenth century taxonomists, at least before those of the

5 3 2 D I C O T Y L . s e u E X O G E N tE .

XII. HELIOTROPIlTM Tourn. inst. 133. t. 57. Linn. gen. n. 179. Juss. gen. 130. Garrtn. fruct. 1. p. 329. t. 68. f . 2. Zam. *7/. f. 91. Lehm. asp~p* 19 ( &rc/. m omnibus spec. nonnuJZ ) Sperm, 0en. /I. germ. tc. ef desert

C a ly x 5 - p a r tit u s a u t r a r is s im e 5 - d e n t a tu s p e r s is t e n s . C o r. h y p o c r a te r i- m o r p h a , fa u c e p e r v ia in te r d u m b a r b a t e , lim b i la c in iis p lic a t u r a sim p lic i v e l r a r is s im e d e n te in te r je c to d o n a t is . S t y lu s b r e v is . S tig m a s u b c o n ic u m . N u cu la e u n ilo c u la r e s ju n io r e s b a s i co h a er en te s d e m u m s e p a r a b ile s b a s i cla u sa e. R e c e p ta c u lu m c o m m u n e n u llu m . S e m in a e x a l b u m i n o s a , e m - b r y o n e in v e r s o , c o t y le d o n ib u s p l a n i s (1). — H erbae a u t s u ffr u tic e s n u n c v a r ie villosae r a r iu s g la b e r r im a e . F o lia in t e g r a a u t d e n t ic u la t a , a lte r n a a u t r a r iu s o p p o s ita . S picae u n ila te r a le s . C or. albae a u t p u r p u r a s c e n t e s , in te rd u m p er e x s ic c a tio n e m o c h r e le u c a e n u n q u a m lu tea e. — S e c tio n e s p lu r e s ( o m n e s ? ) fo rte in g e n e r a c o n v e r te n d a e ?

S e c t io i . Catimas A lph. DC. — S e c t . E u h e l i o t r o p i i s p e c . DC. mss.

Nucbl# 4, ovoideo-triangul^res , intus nempe angulares , doi*so convex#, la- teribus non bifoveolat#. Coroll# faux imberbis ; lobi angusti, #stivatione intra tubum inflexi. Stigma conico-truncatum, apicehispidum, simplex, vel subbifidum. Spicul# bifurcat#, ebracteat#, juniores apice scorpioide# — Nomen ex ?.</.?% deorsum, infra, et , kvto$ lacin u la, quia lacinul# cor. in #stiv. inflex#.

* Antherw prope basim cor olios. Stylus brevissimus } glaber.

1. H. grandiflorum ( Auch.! pi. exs. n. 2362 et 2376, non Schranck ) , herba-

ceum totum molliter villoso-canescenserectum, foliis petiolatis ovalibus obtnsis integerrimis , spicis solitariis ebracteatis, coroll# tubo pubescente calycis lobis lanceolato-linearibus duplo longiore, nuculis subrugulosis glabris. (T) in Ar­ menia legit cl. A ucher! (2). Radix parva sublignosa. Caulis 6-7 poll, longa. Cor-, alba 3-4 lin. lo n g a, lobis oblongis subacutis. (v. s. a cl. inv. )

Fig. 2.5 Part of volume IX page 532 of de Candolle's Prodromus (1845), showing the start of the genus Heliotropium.

next phase, used de Candolle’s system or devised modifications or extensions of it. Among them should be mentioned J. Lindley (1799-1865), A. T.

Brongniart (1801-1876) and S. L. Endlicher 1805-1849). Endlicher’s Genera

Plantarum (1836-1841) covered 6 835 genera of plants, and separated the

Thallophyta (algae and fungi) from the higher plants (Cormophyta). Whereas de Candolle’s sequence of dicotyledon families had started with the Ranuncu- laceae, Endlicher’s commenced with the apetalous families.

The last major natural classification was that of G. Bentham (1800-1884) and J. D. Hooker (1817-1911). Their Genera Plantarum (1862-1883) dealt only with seed-plants, commencing with the Ranunculaceae and related families such as the Magnoliaceae and dealing successively with dicotyledons, gymnosperms and monocotyledons. It described 200 families and 7 569 genera, each in meticulous detail and many subdivided into subgenera and/or sections. The dicotyledons were divided into three great groups: Polypetalae (with free petals), Gamopetalae (with fused petals), and Monochlamydeae (with no petals). Bentham was an extremely accomplished self-trained classical taxonomist who also wrote many important monographs (e.g.

Labiatarum Genera et Species, 1832-1836, in 783 pages) and Floras (e.g. Handbook o f the British Flora, 1858, later editions revised by J. D. Hooker; Flora Australiensis, 1863-1878, in 7 volumes). Hooker, like his father before

him, was Director of the Royal Botanic Gardens, Kew, and explored many parts of the world and wrote several valuable Floras (e.g. The Student's Flora

o f the British Islands, 1870; The Flora o f British India, 1872-1897, in 7

volumes). Their Genera Plantarum, with a general outline based upon that of de Candolle, set new standards in descriptive botany, having been drawn up afresh from the study of herbarium specimens, and it became the standard work in many parts of the world. Indeed, the great herbaria at the British Museum, Kew and Paris are still arranged according to it, and Bentham and Hooker’s Handbook o f the British Flora remained the major British Flora until 1952.

In contrast, rather little progress in the classification of cryptogams was made during this phase. In the immediate post-Linnaean era Lycopodium was classed as a moss, cycads among the ferns, Salvinia as a liverwort, and

Equisetum among the conifers. In 1813 de Candolle was the first to place all

the pteridophytes together as a separate group. In 1843 Brongniart advocated the division of plants into two main groups, Cryptogamae and Phaneroga- mae, while A. Braun in 1864 recognized three groups: Bryophyta (algae, fungi, and bryophytes); Cormophyta (pteridophytes); and Anthophyta (sper- matophytes). Real progress towards the modern system was not made until Eichler’s classification of 1883, which belongs to the next phase. Neverthe­ less, within each of the main groups of lower plants a greater understanding of the degrees of diversity was arising, mainly from the study of microscopic structures and of the life cycles. Naturally, knowledge of algae (and fungi) lagged well behind that of bryophytes and pteridophytes.