578 The American Naturalist. [June,, 
of approaching winter should suggest it. It may be that such species. 
have learned by sad experience that with them it is early seeding or 
none at all. 
In the lowest forms of life there is not even the union of protoplasm 
for the formation of the inactive state. The resting spores of the Bac- 
teria are, as far as we know, ordinary cells, the protoplasm of which 
is unusually protected by a thick cell wall. As we rise in the scale of 
plant life, the points of origin of the two protoplasmic elements become 
more widely separated. In the pond scums (Spirogyra) it may be that the 
contents of adjoining cells unite to form the zygospore. Among 
flowering plants this question brings in review the subject of sexual 
separation, as worked out in the various lines of dimorphism, dichog- 
amy, etc., until we arrive at the dicecious plants. From the bacterium 
resting spores, formed out of the contents of a single cell, the two lines 
diverge until we find their opposite extremities separated by dicecism ; 
a condition in which for the formation of an offspring, corresponding 
functionally with the primordial spore, there must be the union of a 
particle of protoplasm of one community of individuals (tree or herb) 
with another of a separate and otherwise independent community. 
Another parallelism of differentiation may be seen. Among the 
lower forms of life there is but little variation among the units; the 
one reflects the other, and species are founded upon differences that 
are only determined by-using the micrometer. The higher types show 
not only a greater variation in the units, but the communities made 
up of these have their distinct peculiarities. One white pine or 
maple is not like all others of its kind. 
It may, perhaps, be stated as a rule that where there is the greatest 
separation of the sexes, within the limits of the law, there is the great- 
est variation, or the extreme tendency to vary. If the union is between 
different species, there are new lines of variability bestowed upon the 
offspring. If this hybrid unites with another distinct hybrid, it is easy 
to see that the current of tendencies is again made doubly complex, 
and if the offspring is able to bear the load that the law of heredity 
throws upon it (now a broken law), the result will be a set of plants. 
almost as easily turned in their course as autumn leaves floating ona 
sluggish stream, 
Reproduction by union is a deeply laid plan among the higher 
orders of plants. Many plants during one year prepare for its occur- 
rence in the next. Pollen to be shed in the spring is pre- 
pared the previous autumn, and the female germ cells are also already 
made to receive the quickening dust. If we may judge of importance 
