230 DUPLICATION OF GENERATIVE NUCLEI BY MEANS OF 
globular or tetrahedical grains occur; these smaller sterile pollen- 
grains not rarely stick to the fertile ones, so that one may presume. 
that they died at an early stage of development, when the tetrad 
cells had not yet loosened their connexion, were not yet fullgrown; 
fertile pollengrains are still in the majority ; 
3°. sterile pollengrains of different shape and size predominate, poin- 
ting to a partly early, partly late dying off, in addition large globular 
pollengrains, filled with starch-grains, occur: 
4°. the abnormal pollen in its most perfect shape. 
These different stages of pollen-condition are usually the same in 
all the anthers of a flower. It has already been described in the publica- — 
tion, repeatedly mentioned, how the stages may differ somewhat in 
different flowers of an inflorescence. 
b. The habit of the pollen with which we experimented. 
In order to investigate the pollen alive, it, usually taken from some 
flowers lower down and higher up at the inflorescence, was put into a 
drop of water, or, when it was of importance to distinguish the nuclei 
clearly, into a drop of methylgreen-acetic acid and examined under the 
microscope. 
It turned out, that the pollen of Homerus n. D., of Gertrude n. V. W. 
L., of Yellow Hammer n. V. W. L. and of Yellow Hammer n. N. was 
perfectly normal and that less than 10 % Of it was sterile. 
Quite different was the condition of the pollen of Gertrude abn. N., 
which had been induced to flower in January in the glasshouse. This 
pollen proved to be sterile to a considerable percentage. The sterile 
pollengrains were of diverse shape and size. Probably, sporadically, 
large, globular pollengrains, filled with starchgrains, and pollengrains 
with several nuclei occured. This however could not be determined 
with certainty as, through the forcing of the bulbs, the pollengrains 
stuck together to smaller or larger masses, which could not, even not 
by means of preparation-needles, be put apart. 
The pollen of Yellow Hammer abn. N. showed clearly the transition 
from normal to abnormal. All the kinds of pollengrains, mentioned sub 
1°—4° did occur. Depending on the kind of flowers investigated, nor- 
mal fertile grains or mature and immature sterile ones were in the ma- 
jority. Such was never the case with the large, globular pollengrains, 
filled with starch, or with the plurinuclear ones. 
It should be remembered, that one of the inflorescences of Yellow 

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