256 THE AMERICAN NATURALIST. (Vor. XXXIX. 
of the origin and evolution of the endosperm in angiosperms 
there is some evidence in favor of the second possibility. 
Strasburger (:00b) holds that the double and triple nuclear 
fusions in the embryo sac are not true sexual acts even though 
they may involve an important principle of fertilization, namely, 
a stimulus to growth. According to him, sexual processes pre- 
sent two distinct features which he designates as “ generative 
fertilization" and * vegetative fertilization." Generative fertili- 
zation deals with the mingling of ancestral hereditary substances 
in the nuclei and establishes the basis for such characters as 
hold the species true to its past or introduce new qualities as 
variations into the germ plasm. Vegetative fertilization brings 
to the fusion nucleus simply a stimulus to growth such as may 
be given to unfertilized eggs by changes in their physical and 
chemical environment. We might apply this classification to 
many of the examples of asexual nuclear fusions which we have 
discussed, as in the apogamous development of the fern and the 
origin of the paired nuclei in the rusts, and they have the ele- 
ments of vegetative fertilization in Strasburger’s sense. But 
such distinctions are very subtle and it seems rather doubtful 
whether they add much to the clearness of our conceptions. 
The growth stimulus of « vegetative fertilization” is always 
an accompaniment of “generative fertilization” and would be 
expected of any cell unions or nuclear fusions. The pecul- 
iarities of sex lie in the phylogenetic features of the phenomena, 
i. e„ in the union of differentiated gametes with their long evolu- 
tionary history and not in the mere fusion of any nucler at any 
time. 
From this point of view the double fusions of polar nuclei or 
the triple fusions, when a sperm nucleus becomes involved in 
the phenomenon, are of very doubtful sexual nature since no 
phylogenetic connections have been established with the normal 
sexual processes of the spermatophytes. 
irregularities in the process of endosper 
plicate the discussion and make it ve 
ships. 
Indeed, there are many 
m formation which com- 
ry difficult to trace relation- 
Thus nuclear fusions are described in the late stages of 
endosperm formation when several of the free nuclei become 
included in the same cell area by the formation of the cell walls 
