Ze LE “et 
PHYSIOLOGICAL STIMULI AND ITS SIGNIFACANCE 249 
auch die dispermische Befruchtung durch irgend welche abnorme Um- 
stande bedingt werden kann, welche ein aberrantes Eindringen der 
beiden Spermakerne in die Eizelle verursachen” (l.c.p. 17). 
ISHIKAWA (1916) saw the same in the case of Oenothera while a 3d 
male nucleus fused with the endospermnucleus of the same embryo- 
sack. He was unable to observe whether the male nuclei came from one 
or from two pollentubes. In the second case the presence of plurinuclear 
pollengrains in Oenothera must be assumed. In the first case the tips of 
2 pollentubes or of one branched pollentube should have reached the 
eggcell. The latter case might happen among hyacinths as I observed 
in 1919, in the case of the diploid variety Marchioness of Lorne, highly 
branched pollentubes on germinating pollen. ISHIKAWA also mentions 
most of the cases in which either of the following peculiarities were ob- 
served: 1°. 2 or more pollentubes penetrating into one embryosack; 
2°. several male nuclei in one embryosack ; 3°. several male nuclei in one 
pollengrain (Cf. also our publication 1921). 
He does not deem it impossible that triploid mutants arise among Oeno- 
thera as a consequence of dispermatic fertilisation: „At any rate, Ne- 
mec’s view seems to be the most natural one among several hypotheses 
as yet proposed”. 
Osawa (1916) has investigated different varieties of Morus, which 
have been propagated many years asexually, and found several of them 
to be triploid. He imagines them to have arisen from the union of ha- 
ploid with diploid gametes. 
FRISENDAHL (1912) saw in the case of Myricaria germanica once 6 
spermnuclei in one embryosack; he pictures a case of double fertilisa- 
tion. 
These facts strengthen our conclusion that in the hyacinth, fertilisa- 
tion by means of one diploid nucleus or by means of more than one haploid 
nucleus from one pollengrain is not impossible. If we remember, that 
NEMEC draws the two spermnuclei which fuse with the eggnucleus, al- 
most globular, we see no difficulty to assume that the haploid globular 
nuclei, present in the abnormal pollentubes of the hyacinth, are able to 
fertilise an eggcell. 
_ It seems to us illogical, to consider compactness and strong elliptici- 
ty — the usual character of generative nuclei — as the only criteria of 
fertility, the more so, as we have frequently seen at the tip of pollen- 
tubes, both of plurinuclear and of normal pollengrains, a larger globu- 
