652 WorsdelL — A Study of the Vascular System in 
e. g. yuncus and Pistia at the present day, each branch bearing a terminal 
leaf, until such period as the stem-apex began precociously to assert itself 
at each stage and the leaves became displaced from their primitively 
terminal position into a lateral one. This process is repeated in the 
embryonic history of the great majority of Monocotyledons and is the 
explanation of the general and essential grandifoliate habit in this class of 
plants. 
The question has next to be answered whether, for the Angiosperms as 
a group taken by themselves, the grandifoliate or parvifoliate is the most 
primitive form of plant. After a full consideration of the facts of mor- 
phology, especially those relating to the embryonic history of Angio- 
spermous plants, I arrive at the conclusion that the Monocotyledonous and 
grandifoliate structure was characteristic of the primitive Angiosperm. 
Now, my present object in writing this paper is to show that a com- 
parative study of the vascular tissue of certain orders of Angiosperms 
strongly supports the position reached as a result of morphological study, 
viz. that the grandifoliate habit (i. e. a comparatively insignificant stem and 
large sheathing leaves) in Angiosperms has not been derived by reduction 
and degeneration from the parvifoliate habit, but is primitive and original. 
Some would suppose that all geophytes and herbaceous perennials with 
a subterranean stem have been derived by reduction from tall, subaerial, 
woody plants, and that many have again acquired the character of these 
latter. But the facts of embryo and seedling morphology,whichshould,as all 
botanists teach, reproduce that of the ancestry, do not support this view. In 
both classes, Dicotyledons and Monocotyledons, the cotyledons are terminal 
to the axis and the dominating organ of the plant; they are the first organs 
to appear on the scene, the plumule in the majority of cases arising later 
and in a lateral position, which, in the case of Dicotyledons, appears 
terminal, owing to the deep forking of the cotyledon having induced the 
two resulting lobes to separate widely apart from one another, viz. through 
an angle of 180°. It may be said that the early development and terminal 
position of the cotyledons is due to their having become adapted to 
an absorptive function in the embryo-sac ; but there is no evidence for this ; 
and further, if the cotyledons are really lateral and subsidiary to the stem, 
one would expect the latter to become the absorptive organ rather than one 
of the lateral foliar organs, because of its tendency to appear in advance of 
the cotyledons. Nor, again, is it at all likely that such highly advanced 
plants as Dicotyledons should exhibit reduction and degeneration of the 
embryo ; it might be conceivable in parasites and saprophytes, which are 
degenerate in some of their mature organs, but not in plants which in 
no part of their mature organization exhibit degeneration. Again, if the 
single cotyledon has been derived either by fusion of two cotyledons or the 
abortion of the second, one would expect that, occasionally, Monoco- 
