88 JOURNAL AND PROCEEDINGS 
way given expression to their views on the question of relation- 
ship of the different forms to one another have invariably based 
their opinions upon the variations and progression in the mode 
of reproduction of new individuals and the organs which take part 
in this function. This selection is doubtless a wise one, for the 
influence of environment, in the broadest sense of that term, will 
most readily affect the organs that are to the greatest degree con- 
nected with the perpetuation of the species. If this view be cor- 
rect, then the variations and progression observable in these 
organs will fairly well indicate the line along which the evolu- 
tion of plants has taken place. 
The simplest plant form consists of one cell, and increase in 
the number of the individuals in such a ease takes place by the 
division of this original cell—first into two, and when these new 
individuals have reached a certain stage division again occurs. 
This process of division, continued as long as conditions are favor- 
able, will eventually result in the production of an almost in- 
definite number of individuals from the original one. The 
The Glceocapsa, or Chroococcus, will serve to‘illustrate this mode 
of reproduction. 
In the foregoing process only one cell takes part, and the 
individual at any time consists of but a single cell. In the course 
of time the individual, by two or more cells failing to separate 
from one another, becomes a more complex structure, the simplest 
form of which is a thread of cells. With this increase of com- 
plexity of structure there arises a differentiation in the mode of 
reproduction, and very soon we find two cells taking part in this 
function. 
In the Spirogyra, which consists of threads of cells floating 
in water, the cells of adjacent threads put out processes In such a 
way that those of the cells in the different threads meet one an- 
other and the contents of one cell pass into the other, and the con- 
tents of the two fuse together and a new individual is formed, 
which passes into a resting condition. In this simple operation 
we have the beginning of sexual reproduction. ‘In external ap- 
pearance the two cells whose contents fuse together are not dis- 
similar, so that structurally there is no apparent differentiation. 
