IN ANIMALS AND IN PLANTS 175 
geny of any higher sporophyte is a much less essential incident in the 
whole development than that in any higher animal: the embryogeny of 
a higher animal is at best only comparable with the initial embryogeny 
of a plant where the embryo is still enclosed in the tissue of the parent: 
it has no counterpart corresponding to that continued embryology which is 
so long maintained in the apical region of the plant-body. 
Secondly, the sporophyte is now believed to be itself an intercalated 
phase, which has assumed increasing proportions in the course of descent, 
while the function of spore-formation, which comparison tells us was the 
initial function of the sporophyte, has been proportionally delayed. If 
this be true, so far from the first formed parts being in their present 
form the prototypes, they would be more correctly recognised as derivatives, 
modified, or it may be transformed, during later evolutionary periods. . 
The absence of strict analogy between the embryogeny of the higher 
animals and the higher plants is further illustrated in relation to the theory 
of germinal layers. Following on the experience of animal embryologists 
who found that definite regions of tissue of the mature animal body are 
referable in origin to definite germinal layers of the embryo, Famintzin 
undertook to prove that the same holds for the definite systems of 
epidermis and vascular tissue in the Angiosperms. It is true that the 
origin of the epidermis and of the central stele gives some countenance 
to such a view, though even in these it is not difficult to quote exceptions 
where that regular mode of origin does not exactly apply. But the 
question becomes critical with regard to those parts of the vascular system 
which pass from the stem into the leaves: do these originate from the 
plerome-system of the axis, as by the theory of germinal layers they ought 
to do? As De Bary pointed out,! this could not be otherwise effected 
than by outgrowths of the plerome pushing between the other layers of 
the young forming leaf. But as a matter of fact, they are derived from 
the primary periblem, and definite bands of this tissue show the corre- 
sponding differentiation, by which means the vascular system of the leaf is 
connected with that of the axis. This almost forgotten discussion is quoted 
here as an example of an attempt, actually made, to impose an embryo- 
logical idea derived from the study of animals upon the embryology of the 
higher plants; and it shows how, when submitted to the test of detailed 
observation, it has been rejected. It must be clearly understood that such 
comparisons deal only with distant analogies, and that for reasons such as 
those already explained the methods and arguments of animal embryologists 
are not transferable to the embryology of the sporophyte of plants. In 
point of fact, hitherto plant-embryology owes little to animal embryology 
beyond the confusion of thought which follows on fallacious comparisons. 
The success of Naegeli and Leitgeb in recognising and delineating the 
apical cell, and the regular succession of its segmentations in various 
plants, turned the course of accurate observation about the middle of 
\ Comp. Anat. Engl. Ed., p. 23. 
