922 KEPORT— 1900. 



Mor2)1iology. 



If inquiry te made as to the cause of the great advance iu the recognition of 

 the true affinities of plants, and consequently in their classification, which distin- 

 guishes the nineteenth century, I would refer it to the progress made in the study 

 of morphology. The earlier botanists regarded all the various parts of plants as 

 'organs' in relation to their supposed function ; hence their description of plants 

 was simply 'organography.' The idea of regarding the parts of the plant-body, 

 not in connection with their functions, but with reference to their development 

 and their mutual relations, seems to have originated with Jung in the seventeenth 

 century (1687) : it was revived by 0. F. Wolff about seventy years later (1759), 

 but it did not materially aflect the study of plants until well on in the nineteenth 

 century, after Goethe had repeatedly written on the subject and had devised the 

 term ' morphology ' to designate it. For a time this somewhat abstract mode of 

 treatment led to mere theorising and speculation, so much so that the years 

 1820-1840 will always be stigmatised as the period of the ' Naturphilosophie.' 

 But fortunately this time of barrenness was succeeded by a veritable renascence. 

 Robert Brown and Henfrey in England ; Brongniart, iSt. Hilaire, and Tulasne 

 in France ; Mohl, Schleideii, Naegeli, A. Braun, and, above all, Hofmeister in 

 Germany, led the way back from the pursuit of fantastic will-o'-the-wisps to the 

 observation of actual fact. Instead of evolving schemes out of their own internal 

 consciousness as to how plants ought to be constructed, they endeavoured to 

 discover by the study of development, and more particularly of embryogeny, how 

 they actually are constructed, with the result that within a decade Hofmeister 

 discovered the alternation of generations in the higher plants; a discovery which 

 must ever rank as one of the most brilliant triumphs of morphological research. 



With the knowledge thus acquired it became possible to determine the true 

 relations of the various parts of the plant-body; to distinguish these parts as 

 ' members ' rather than as ' organs ; ' in a word, to establish homologies where 

 hitherto only analogies had been traced — which is the essential difference between 

 morphology and organography. 



The publication of the ' Origin of Species' profoundly aftected the progress of 

 morphology, as of all branches of biological research : but it did not alter its 

 trend ; it confirmed and extended it. We are not satisfied now with establishing 

 homologies, but we go on to inquire into the origin and phylogeny of the members 

 of the body. In illustration I may briefly refer to two problems of this kind 

 which at the present time are agitating ihe botanical world. The first is as to 

 the origin of the alternation of generations. Did it come about by the modifica- 

 tion of the sexual generation (gametophyte) into an asexual (sporophyte) ; or is the 

 sporophyte a new formation intercalated into the life-history ? In a word, is the 

 alternation of generations to be regarded as homologous or as antithetic r I am 

 not rash enough to express any opinion on this controversy ; uor is it necessary 

 that I should do so, since the subject has twice been threshed out at recent 

 meetings of this Section. The second problem is as to the origin of the sporophylls, 

 and, indeed, of all the various kinds of leaves of the sporophyte in the higher 

 plants. It is suggested, on the one hand, that the sporophylls of the Pteridophyta 

 have arisen by gradual sterilisation and segmentation from an unsegmented and 

 almost wholly reproductive body, represented in our day by the sporogouium 

 of the Bryophyta ; and that the vegetative leaves have been derived by further 

 sterilisation from the sporophylls. On the other liand, it is urged that the 

 vegetative leaves are the more primitive, and that the sporophylls have been derived 

 from them. It will be at once observed that this second problem is intimately 

 connected with the first. The sterilisation theory of the origin of leaves is a 

 necessary consequence of the antithetic view of the alternation of generations ; 

 whilst the derivation of sporophylls from foliage-leaves is similarly associated with 

 the homologous view. Here, again, exercising a wise discretion, I will only 

 venture to express my appreciation of the important work which has been done in 

 connection with this controversy — work that will be equally valuable, whatever 

 the issue may eventually be. 



