608 D. T. MACDOUGAL 
the constituents of development especially with regard to the vegetal 
organism. The first method of multiplication of individuals or 
colloidal masses undoubtedly consisted of simple fragmentation 
resulting from the accumulation of a mass too great to be held together 
by surface tension, and the separation of these masses must have 
been accomplished, or made possible by flotation which continues 
to be one of the most efficient agencies in the dissemination of plants, 
a fact specially emphasized by the results of our studies upon the 
revegetation of the Salton Basin. 
An early specialization of structure probably rested upon the 
reduction of portions of the self-renewing colloidal masses from the 
suspended condition of a sol to the condition of a gel, and doubtless 
the limiting membranes of protoplasmic masses depend upon this 
process. Likewise some form of centrum resulted from congelation 
processes by activities of a nature elementary to the relations of the 
nucleus and cytoplasm in the modern cell. 
Wherever portions of the colloidal mass came into contact with 
solid substances gelation or aggregation ensued, and the masses of 
material thus differentiated would give form and stability in place, 
representing the earliest form of anchorage organ. In this as well 
as in other features of the plant, evolutionary development was slow 
so long as the monotonous conditions of an aquatic habitat were to 
be met. Very simple processes or extrusions from a cell or coenocyte 
of this general nature are still to be encountered among certain algae. 
As soon, however, as it was left stranded by the disappearance of 
the shallow waters in which it may have lived, or was lifted above the 
water level by any means, the diversified conditions encountered by the 
organism, including desiccation, exercised a differentiating effect on the 
root-organ scarcely less marked than those which may be ascribed to 
the same agency in the shoot. The necessity for anchorage was no 
less, but now the nutritive substances no longer bathed the entire 
body but were present only in hygroscopic solutions on the soil 
particles with a vertical distribution not uniform, and with much 
horizontal irregularity. Survival depended upon the formation of 
specialized tracts for absorption, and conduits for the transport of 
solutions from the organ of fixation to other parts of the living mass. 
It is to be noted, however, that the modern root arose anew from the 
