100 A CYTOLOGICAL INVESTIGATION OF SOME SPIECES 
to cross Black Cheribon cane with other species of the genus Saccha 
rum, supposed to be immune against sereh. They consequently sought 
the solution in the obtention of species-hybrids. In 1893 WAKKER !) 
wrote: 
„We must try to obtain one or more varieties, preferable in some res- 
pect to the ones, now in our possession.” 
The respects, first to be kept in mind, are: 
1°. a higher percentage of obtainable sugar; 
2°. a greater resistance against disease. 
In the same year WAKKER proceeded to cross Cheribon sugarcane, 
with Kassoer-cane, found to grow feral at the foot of the Tjerimai, and, 
by him, supposed to be a wild Saccharum-species. From this cross 13 
plants were obtained. 
In the year 1890 Kosus travelled in British-India with the object in 
view to obtain different kinds of sugarcane fit to be planted on the is- 
land of Banka. All kinds which remained free of the dreaded disease 
on that island should subsequently be sent to Java. 
In his report of this trip he writes 9): 
„A large number of the British-India Cane-varieties seem to me to 
belong to ancther species of Saccharum. We may possibly succeed in 
crossing these with our kinds of sugar-cane and thus obtain hybrids, 
which in addition to the high sugar-content of both parents combine 
the dimensions of the one and the resistance of the other.” 
Among the different forms of sugar-cane which he introduced 
into Banka were Chunnee and Ruckree, differing greatly in habit 
from Saccharum officinarum. He thought it highly probable that these 
would be immune against sereh and expected much from crosses in 
which they took part. After having been cultivated at Banka, where 
they remained healthy, they were transported to Java where the Stri- 
ped Preanger was now crossed for the first time with Chunnee ?). The 
cross was successful. From that time crossing of species has been execu- 
ted repeatedly with the result that plants have been obtained with a 
good sugar-content and a strong resistance against sereh. Saccharum 
officinarum, Chunnee and Kassoer have always participated in these 
crosses. A great percentage of the species-hybrids, so obtained, are per- 
1) J.H. WAKKER, Onze zaadplanten van het jaar 1893. Archief I, p. 386. 
*) J.D.Kosus, De zaadplanten der kruising van Cheribonriet met de Engelsch- 
Indische varieteit Chunnee. Archief VI. 1898, p. 625. 
