AND SPECIES-HYBRIDS WITHIN THE GENUS SACCHARUM 311 
72 univalent chromosomes in thePMC. The meiotic divisions were al- 
ways entirely abnormal. No fertile pollen was ever formed. In the fe- 
male line also, these hybrids were quite sterile. 
2°. À varying number of chromosomes pair. Such a case was descri- 
bed by FARMER and Dicpy !) in the Fern hybrid: Polypodium Schner- 
deri, the product of a cross between P. aureum with haploid approxi- 
mately 34 chromosomes and, P. vulgare var: elegantissimum with ap- 
proximately 90 chromosomes in the haploid phase. The diploid chro- 
mosomenumber of the hybrid was approximately 124. 
The prophase of the reduction-division usually showed 95— 105 chro- 
matine-elements. The number of chromosomes which proceeded to pair 
was not constant; in no case all of the 34 chromosomes of the one pa- 
rent-species paired with 34chromosomes of the other parent-species, 
but rarely no pairing whatever took place. At the division of the spore- 
mothercells all kinds of irregularities occurred, but rarely tetrads were 
formed. The hybrid is sterile. 
3°. All chromosomes of the one parent-species of the hybrid pair 
with part of the chromosomes of the other parent-species, while the 
rest of the chromosomes remain single. The first described, and most 
generally known example of this class,is the hybrid,described by ROSEN- 
BERG 2), between Drosera longifolia with haploid 20 chromosomes and 
D. rotundifolia with haploid 10 chromosomes. The hybrid, D. obovata, 
possesses 30 chromosomes in its somatic cells, while in the prophase of 
the division of the PMC 10 gemini and 10 single chromosomes occur. 
ROSENBERG deemed it probable that 10 chromosomes of D. longifolia 
had paired with all of the 10 chromosomes of D. rotundifolia, and that 
the 10 single chromosomes represented the rest of the longifolia-chro- 
mosomes. In the metaphase he found 10 gemini and 10 unpaired chro- 
mosomes, which clearly were half as large and were usually situated at 
the borders of the spindle, above or below the aequator. The chromoso- 
mes of the gemini moved regularly towards the poles, while the single 
chromosomes were distributed over the poles, according to chance, so 
that the two poles obtained a different number of them. Sometimes 
1) J. B. FARMER and L. Div. On the Cytological Features exhibited by 
certain Varietal and Hybrid Ferns. Annals of Botany. Vol. XXIV. 1910, p. 1910 
2) O. ROSENBERG. Cytologische und morphologische Studien an Drosera lon- 
gifolia x rotundifolia. Kgl. Svenska Vetenskapsakademiens Handlingar. Bd. 43. 
ice ba 909. 
