180 ANGIOSPERMS. 
manifestation of a growth stimulus. Vegetative fecundation according 
to this interpretation finds its parallel in such phenomena as described by 
Klebs (’98, 1900), Loeb (’99, ’or) and Nathansohn (1900), in which, 
by means of physical or chemical stimuli, such as increased tempera- 
ture or an increase of the osmotic power of the surrounding fluid, 
unfecundated egg-cells have been made to develop parthenogenetically 
through certain embryonic stages. According to the view of Stras- 
burger, therefore, sexual reproduction embraces fundamentally two 
great and far-reaching factors, namely, the union of hereditary ele- 
ments and the imparting of a growth stimulus. In the fusion of a 
male nucleus with the endosperm nucleus, only one of these factors, 
the stimulus to growth, is manifested, since the interrupted growth of 
the endosperm is enabled tocontinue. The result is the same whether 
the second sperm nucleus unites with the endosperm nucleus or not, 
and furthermore because the endosperm is not an individual in the 
sense that the embryo sporophyte is an individual. It is further true 
that the endosperm nucleus may divide and give rise to several nuclei 
before the contents of the pollen tube are discharged into the embryo- 
sac, and in case that no pollen tube reaches the embryo-sac, these same 
endosperm nuclei never continue their development. It is reasonable 
to conclude, therefore, that a growth stimulus may be imparted to 
the endosperm by the act of fecundation in the egg-cell, just as the 
vegetative tissue of certain parts of the pistil are stimulated to growth 
by the presence of the pollen tube, 
Many who agree with Strasburger may probably not consider it 
necessary or advisable to use the term ‘‘ vegetative fecundation.” The 
author does not see the necessity of associating the idea of fecundation 
with this process of nuclear fusion, for the reason that nuclear fusions 
in vegetative cells do not signify an act of fecundation. In the light 
of all the known facts, it seems that we have to do here with purely 
vegetative fusions, and that we are not justified in attributing to such 
nuclear fusions the idea of sexuality. Although the upper polar — 
nucleus is the sister of the egg-nucleus, it does not necessarily follow 
that the former is also a female nucleus, since it is certainly not true that 
the sister cells of egg-cells are even potential gametes. If such an 
assumption were accepted, then the ventral canal-cell of the arche- 
goniates might be considered an egg-cell, a doctrine to which the 
author can not, as yet, subscribe. 
