24 
R. H. Compton. 
evolution than that of the “ disposition altevne .” For similar 
reasons Chauveaud’s theory differs from Gerard’s “triple hypothesis 
of identity (of vascular strands as between root and stem), doubling 
and rotation ” : and the same applies to any theory based on the 
divergeant as an anatomical unit. Further it is clearly incompatible 
with the “contact” theory of Sterckx. Its relation to Miss 
Thomas’ theory of the double bundle and dichotomy is of interest’ 
The different types of double bundle and the “ perfect series of 
intermediate cases ” are brought into relation with one another as 
different phases of an evolutionary cycle which the vascular strands 
may pass through, both in time at one and the same level, and in 
space (as we ascend the hypocotyledonary axis) at one and the 
same time. The tendency of Chauveaud’s work is to indicate that 
appearances of doubleness in the vascular strands of cotyledons are 
related to their direct connection with the “ disposition altevne ” of 
the root; and this runs counter to Miss Thomas’ view that they are 
reminiscent of ancestral dichotomy. 
The greater part of Chauveaud’s detailed work is directed to 
establishing the series of phases of structure, and is carried out by 
means of sections of the same part of the seedling at different 
stages of development. The ordinary investigation of the transition 
phenomena is carried out by means of sections of different parts of 
the seedling at the same stage of development. Both methods of 
study are legitimate and useful, and the validity of the latter is 
unaffected by Chauveaud’s demonstrations, which, however, throw 
a flood of light on the processes observed. 
LITERATURE CITED. 
f 
1. C. E. Bertrand et F. Cornailie. “Etude sur quelques caracteristiques 
de la structure des Filicinees actuelles.” Trav. et 
Mem. Univ. de Lille, t. X, Mem. no. 29, 1902. 
2. G. Bonnier. “ Sur l’ordre de formation des elements du cylindre central 
dans la racine et la tige.” C. R. Acad, des Sci., 
t. CXXXI, p. 781, 1900. 
3. ,, “ Sur la differentiation des tissus vasculaires de la feuille et 
de la tige.” Ibid, p. 1276, 1900. 
4. G. Bonnier et L. du Sablon. “ Cours de Botanique,” t. I, pp. 382, 424, 
1901. 
5. G. Chauveaud. “ L’appareil conducteur des plantes vasculaires et leg 
phases principales de son evolution.” Ann. Sci. Nat. 
(Bot.) ix e ser., t. XIII, p. 113, 1911. [And the earlier 
papers from 1901 onwards quoted therein]. 
“ Du collet dans les plantes.” Ann. Sci. Nat. (Bot.), iii' ser., 
-t. XIII, p. 5, 1849. 
6. D. Clos. 
