ORIGINATION OF SELF-GENERATING MATTER 609 
vegetative axis, and is therefore not directly derived from the primi- 
tive anchorage organs described. 
The present occasion does not warrant a discussion of the evolu- 
tionary development of the vegetal.organism from the colloidal mass 
to the gametophyte, now represented by the prothallium of ferns 
and their allies. Neither is it necessary to recall details of plant 
anatomy further than to point out that the earlier forms of plants, 
co-ordinately with the monotonous conditions offered by their ac- 
quatic habitats, showed no differentiation of tissues comparable 
with that of the axis of the modern seed-plant, and that their 
flattened bodies were for the most part closely appressed or adherent 
to the substrata. The development of the sexual type of reproduc- 
tion in such forms had been followed by a habit of formation of the 
sexual organs separately, perhaps some distance apart on the upper or 
lower surfaces of the body. In the functionation of such organs the 
two kinds of protoplasts representing the sexual elements would be 
set free at the surface of the body and accomplish union while swim- 
ming freely, or in higher stages of development, the one representing 
the egg-cell would remain in place, while the fertilizing protoplast, 
or spermatozoon would find its way to it. In either case free water 
was absolutely necessary for reproduction. The body of the plant 
might be partially or completely immersed, or it might have only a 
thin film coating the surface, through which the sexual elements must 
move, but in either case the plant could not survive away from the 
margins of streams, seas, and lakes, or up out of the moist lowlands, 
or beyond the borders of rainy regions. 
The thallose forms carrying on sexual reproduction do not appear 
to have been capable of the morphological development which might 
have gained them independence from the water, and this freedom 
was gained only after a secondary, asexual generation came into 
existence. 
In the general movement which finally resulted in a land flora, 
the fertilized egg held in the body of the thallus would germinate 
in place, developing into a vegetative structure (the sporophyte) 
unlike the thallus which bore the egg. Then cells were cut off, or 
separated from the body of this alternate generation, known as the 
sporophyte, which had the power of developing into thalli like the 
