520 THE CYTOLOGY OF THE SUGARCANE 
mal reduction division does occur in it, seems to be contrary to the 
view that there should exist a relation between male sterility and irre- 
gular reduction-division. This need not be however. It is almost cer- 
tain, that sterility in the case of sugarcane can, as in the case of other 
plants, have different causes. We also see the first appearances of steri- 
lity arise at different times in the development of the inflorescence. We 
know kinds of sugarcane, which never form inflorescences and as a 
consequence are absolutely sterile; others are sterile because in the 
spikelets of the inflorescences no or rudimentary sexual organs only 
are formed; sometimes these Ri abnormal that the formation of 
sporogenous cells sets out; it may also happen that pollen-mothercells 
are formed, but that these degenerate at an early age; sometimes pollen 
dyads only are formed and, through rounding off of these, pollengrains, 
which prove to be sterile; in other cases approximately normal tetrad- 
cells arise, but the pollen becomes sterile and the anthers do not open; 
while finally there are kinds which sometimes form fertile, sometimes 
sterile pollen and which sometimes show a regular, sometimes an 
irregular chromosome-reduction. 
This last category puts the question how it is that the reduction-divi- 
sion sometimes runs a perfectly regular, sometimes a quite irregular 
course. The answer is, that external conditions have a great influence 
on the reduction division. The factor of which we must think first and 
which probably has a very unfavorable influence, is dryness. During 
and shortly before the time of flowering of the sugarcane, rather long 
periods of dryness are apt to occur in the coastal region of East- 
Java. 
These can have such a retarding influence that the inflorescences of 
the sugarcane are not able to push aside the leaf-sheaths which sur- 
round them; it may also occur that in the case of canes which under 
normal conditions are satisfactorily fertile in the male line, the inflo- 
rescence puts in an apparently normal appearance, but that the an- 
thers remain closed. These however are extreme cases, which occur 
only in times of exceptional drought. 
It was said, in the first communication, that Green German New Gui- 
nea cane almost always showed an irregular reduction division. In 
some preparations even a completely abnormal division was seen, such 
a one as ROSENBERG has named a , halbheterotypische Teilung’’. All 
the material of G. D. N. G. had been collected during the drought of 
