PHYTONIC VIEWS 135 



X. 



whole shoot regarded as being mainly composed of leaves, but some even 

 contend that the axis has no real existence as a part distinct from the 

 leaf bases. 1 



This view in its general form represented the leafy plant as constructed 

 on a plan somewhat similar to that of a complex zoophyte. It has more 

 recently culminated in the writings of Celakovsky and Delpino. The former 

 in his theory of shoot-segments (" Sprossgliedlehre ") starts from the position 

 that the plant is composed of morphological individuals ; the cell, the shoot, 

 and the plant-stock are recognised as such. The stock is composed of 

 shoots and the shoot of cells. Braun recognised the shoot as the individual 

 par excellence; between the cell and the shoot is a great gulf, which has 

 not yet been filled ; " between the cell and the bud (shoot) there must 

 be intermediate steps, the limitation of which no one has succeeded in 

 denning"; the long sought-for individual middle step is the shoot-segment 

 (Spross-glied), which is neither leaf only nor stem-segment only, but the leaf 

 together with its stem-segment. Now this reasoning appears to involve a 

 mistaken method of morphology ; the intermediate step must occur ; we will, 

 therefore, discover and define it. The definition of it consists in the draw- 

 ing of certain transverse and longitudinal lines partitioning the shoot, lines 

 which in the sporophyte have no existence in nature ; the assumed necessity 

 of partitioning the shoot into parts of an intermediate category between the 

 whole shoot and the cell brings these assumed limits into existence. 



Notwithstanding the ingenuity of the theory as put forward by 

 Celakovsky, in the absence of any structural indication of the limits of 

 the shoot-segments in the vast majority of cases the theory does not appear 

 to be sufficiently upheld by the facts. 



An extreme, and indeed a paradoxical position has been taken on this 

 phytonic question by Delpino. As a consequence of his studies on 

 phyllotaxis he concluded that the axis is simply composed of the fusion 

 of the leaf-bases ; that the leaves are not appendicular organs, but central 

 organs; that an axis or stem-system does not exist, and accordingly that 

 the higher plants are not cormophytes at all, but phyllophytes. 



The second view, that the axis and leaf are the result of differentiation 

 of an indifferent branch-system, of which the limbs were originally all alike, 

 has lately been brought into prominence by Potonie. 2 Taking his initiative 

 from the branching of the leaves in early fossil Ferns, he recognises the 

 frequent occurrence of overtopping (" Uebergipfelung "), that is, the gradual 

 process of assertion of certain limbs of a branch-system over others; in 

 the branching of Fucoids he finds an analogy for his observations on 

 Fern-leaves, and draws the following conclusion, that " the leaves of the 



1 Delpino, " Teoria generale della Filotassi." FY>r ref. see Bot. Jahresbr., viii., 1880, 

 p. 118; also vol. xi., 1883, p. 550. 



- Lehrbuch d. Pflanzenpalaeontologie, pp. 156-159. Also Ein Blick in die Geschichte 

 a. Bot. Alorph. und d. Pericaulomtheorie, 1903, p. 33, etc. It was, however, suggested 

 previously by myself, Phil. Trans., 1884, part ii., p. 605. 



