220 



The Plant World. 



this power of absorption of light rays is to be assigned to chloro- 

 phyll, but preceding the formation of this very intricate and un- 

 stable substance there may have occurred a series of other com- 

 pounds acting as screens capable of absorbing rays from the lower 

 part of the spectrum, of which the reddish and bluish pigments 

 of the lower algae are surviving examples. Many disintegration 

 products constituting the reds and blues of plant tissues sustain 

 physical relations of a similar character to sunlight 



ENVIRONMENTAL RELATIONS 



It is not possible to form any rational conception of living 

 matter without including its environmental relations These 

 become of the utmost importance at the moment of formation of 

 self-generating matter, and it may be assumed with perfect 

 safety that of all the possible synthetic processes, only those 

 which ensued in the presence of a medium which furnished sub- 

 stances suitable for building material could survive Further- 

 more, when the accumulation of this material and its bpecializa- 

 tion is considered, it is apparent that successful origination oc- 

 curred only on solid or semi-solid substrata rather than in un- 

 differentiated solutions in open waters. Still, an abundance of 

 this liquid would be of great importance to the colloidal masses 

 which we may think of as the earliest living things; and, as will 

 be shown presently, water has continued to be the most important 

 of all the constituents of environment, 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 especially empha- 

 sized by the results of our studies upon the re-vegetation of the 

 Salton basin. 



Wherever portions of the colloidal mass came into contact 

 with solid substances, gelation or aggregation ensued, and the 

 lavers of material thus differentiated would give form and sta- 

 bility in place, representing the earliest form of anchorage organ, 

 which must have been the first member of the vegetative axis 

 to take on definite functions and structure In this, as well as 



