THE TAST HISTORY OF MONOCOTYLEDONS 2ig 



of the leaf as a purely lateral appendage to an axis. We are misled 

 all along the line into believing these secondary modifications to be 

 the original types'' (PI. 111. fig. i). 



From the embryonic segmentation and the dominant cotyledons 

 the usual view as to the appendicular nature of the leaf is wrong. 

 The plant is built up of a number of individuals (phytons) by 

 " ana[)hytosis," or sympodial aiTangement. On this view monocoty- 

 ledons are the older. Angiospermous plants may be placed in one 

 of two categories according to their habit, viz. : — 



Grandifoliate plants (monocotylous), stem subsidiary, with bundle- 

 system like that of the leaf, reduced internodes, leaves dominant, 

 closely succeeding, with wide sheathing base ; e.g. palms, water-lilies. 



Parvifoliate (dicotylous), stem dominant, bundle-system differing 

 from that of the leaf, elongated internodes, small leaves, unsheathed 

 bases ; e.g. elm, wall-flower. 



The grandifoliate is the more primitive, and is due to the 

 precocious assertion of the axis, displacing the terminal cotyledon, 

 which is constantly repeated and gives rise to the short 

 internodes. 



Dr. Worsdell points out in regard to the fusion or abortion of one 

 cotyledon to account for the deviation of the monocotylous from the 

 dicotylar type, that in no instance has a monocotylous plant been 

 found to develop a bifid cotyledon or two cotyledons. On the 

 other hand, the converse is found where amongst dicotyledons one 

 is found. 



This is held to be a reversion. Bifurcation of cotyledons is 

 common, and the polycotyledonary form seems to be the direction 

 evolution is taking. 



Thus we come to the novel view recently promulgated by 

 Dr. Worsdell as follows : " Hence I hold that the presence of two 

 cotyledons in dicotyledons is merely an illusive appearance. There 

 is only one cotyledon, as in monocotyledons \ this has become so 

 deeply bifurcated in the great majority of cases as to give the appear- 

 ance of two distinct leaves." 



The sympodial arrangement of the stem and leaves is a recapitula- 

 tion of that of the seedling monocotyledon, and as such lends 

 support to their relatively primitive character. 



In regard to the ancestry of Angiosperms generally, Dr. Worsdell 

 remarks : — 



" I feel more and more inclined to hold the view that Angio- 

 sperms have developed directly from an ancestor belonging to the 

 Bryophyte level, and that they have not come from either Gymno- 

 sperms, Pteridosperms, or Ferns. On the other hand, it is quite 

 possible that they have descended from a fern-like ancestor." 



The tendency of Dr. Worsdell's view is thus largely in the direction 

 of the point reached by Celakovsky and Bower. 



Ontogeny does not always visibly repeat phylogeny. In seedling 

 structure some stages are omitted, and there is no room for scattered 

 bundles. The adult, however, should include all previous stages. 



