The Determinative Action of Environic Factors Upon Neobeckia acquatica Greene. 265 
respect to the various organs. (See Goebel, Organography of Plants. 
Part I, pag. 45 and 145. 1900.) 
The fact that the structure of the leaves of any part of the series 
is generally of an obvious suitability for activity under the seasonal 
conditions in whicli tliey usually are formed has led many writers to 
assign a directly determinative action to the environment. The coin- 
cidence of amplitude of ränge in intensity of environic conditions and 
of correlated diversity of structure, as exemplified by Bidens Beckii, 
Cabomba, Ranunculus delphinifolius, Proserpinaca palustris, 
Sium cicutaefolium, and of Neobeckia the subject of the study descri- 
bed on the following pages, might be one of simple survival by fitness, or on 
the other liand, fitness might in itself be induced by the agencies encountered. 
Any consideration of the matter raises the question at once as 
to how far the various forms of a polymorphic series are morphologi- 
Fig. 1. Seedlings of Sium cicutaefolium grown as terrestrials. 
cally determinative, following an unmodifiable proceedure, and to what 
extent the morphogeny of the metameres may be modified by mani- 
pulation of the external conditions affecting their development. The 
results of Shull cited above seem to show that the ontogeny of Sium 
is independent and that external conditions may be modified to increase 
the ränge of variability or to cause rejuvenescence at any stage, yet 
their influence goes no farther. 
This Variation may be illustrated by some results which the author 
obtained with Sium, in the New York Botanical Garden in 1903. Two 
series of germinating seeds in soil were made. One was treated in 
the ordinary manner and the other was submerged to a depth of 10 cm 
in water. 
The seedlings germinated as terrestrials grew more rapidly than 
those under water and had a main root 2 to 3 cm long with a few 
lateral branches, and had also some adventitions roots arising frorn the 
