1918] NOTHNAGEL—FERTILIZATION 145 
In 1900 GUIGNARD (9) found that in some cases the polar nuclei, 
the upper one of which he said was analogous to the egg, fused 
before the entrance of the pollen tube, and that when the male 
nuclei entered the sac, they entered into fusion so quickly that, in 
some species, one rarely saw them free. In Tulipa he was able to 
follow the contour of the three nuclei entering into the fusion 
nucleus some time after their coming together, and even after the 
membranes had disappeared at their surface of contact. 
As a result of investigations in various groups of angiosperms 
by GuIGNARD (6, 7, 8, 9, 10), NAWASCHIN (15), STRASBURGER 
(17, 18), and others at this time, it was generally concluded that 
double fecundation was normally found in angiosperms and that 
the uniting of the male nucleus with the polar nuclei was in the 
nature of a pseudo-fecundation whose function was to stimulate 
the formation of ‘‘albumen.”’ 
Ernst (3), investigating fertilization of Paris quadrifolia and 
Trillium grandiflorum, found that the two polar nuclei were fused 
before the male nucleus united with them, and at times a spirem was 
formed previous to the entrance of the sperm, showing that the 
male nucleus was not necessary to stimulate division. At other 
times the spirem was not formed until the three nuclei were fused, 
in which case he was unable to discern which part of the chromatin 
was contributed by the various nuclei. He also stated that it was 
not safe to rely upon the number of nucleoli found in the fused mass 
to ascertain whether fertilization had taken place or not. In the 
fecundation of the egg there was a complete blending of the 
substances, and at cross segmentation he failed to find the arrange- 
ment of the chromatin into two groups. 
STRASBURGER (17, 18) used the terms generative and vegetative 
fertilization, the latter being applied to the triple fusion. The 
union of the sperm, either with the egg or with the polar nuclei, 
functioned as a stimulus. 
In 1911 Coutrer (2), after reviewing the literature on endo- 
sperm formation, stated that since endosperm may form without 
the fusion of the sperm or even of the second polar nucleus, these 
being simply supplementary, there seemed to be no reason why 
“there should be any hesitation in recognizing the endosperm as 
gametophyte.”” He concluded that “the product of such fusions is 
