en 
AND SPECIES-HYBRIDS WITHIN THE GENUS SACCHARUM 329 
markable that here also, the increase of the chromosomenumber seems 
to have a favorable effect on the development of the hybrid indivi- 
duals: From the cross S. officinarum X S. spontaneum hybrids arise, 
which ‚with very few exceptions, are, as far as male fertility is concerned 
considerably more fertile than the S. officinarum-individual used in 
the cross. 
The S. officinarum-individuals, used for crossing, were either entire- 
ly sterile in the male line or gave but a very small quantity of pollen, a 
small percentage only of which, more over, was normally developed. 
The low fertility of these sugarcane-varieties is also shown by the fact, 
that where they were used as motherplants in the crosses, self-fertilisa- 
tion almost never occurs, so that castration is superfluous. 
WINGE 1) has pointed out, that, in as much as among Musa sapien- 
hum races occur, which possess 8, 16 and 24 chromosomes in the ha- 
ploid phase, the chromosomenumber 24 cannot have arisen by dou- 
bling from races with a lower chromosomenumber. The number 16 can 
have arisen by doubling of the number 8, doubling of 16 however would 
give 32 and not 24. TISCHLER ?) deems it possible, that a race with the 
* haploid chromosomenumber 24 may have arisen by dispermatic ferti- 
lisation from a race with 16 chromosomes in the haploid phase. Disper- 
matic fertilisation would give a race with 48 as the diploid number of 
chromosomes and, after reduction, gametes with 24 chromosomes 
would be formed. WINGE, to the contrary, thinks that in a race, arisen 
by dispermatic fertilisation, normal reduction division would frequent- 
ly fail to occur. 
It is true, that it is hard to imagine anything else, than that at the 
division of the gonotokonts of individuals arisen by dispermatic ferti- 
lisation, one set of chromosomes would remain unpaired, as in the 
case of the heterodiploid hybrids. | 
Wince thinks it possible that doubling of the chromosomenumber 
should give rise to plants of larger size, but these would, in other res- 
pects, differ but little from the plants from which they originated. As 
plant-forms with higher chromosomenumbers differ however in many 
characters from related forms with lower numbers, he deems their 


1) ©. Wince. The Chromosomes. Their numbers and general Importance. 
C. R. des Travaux du Laboratoire de Carlsberg. 13me Vol. 1917. 
2) G. TiscHLER. Chromosomenzahl, — Form und — Individualität im Pflan- 
zenreiche. Progressus Rei Botanicae. 1916, p. 227. 
