AND SPECIES-HYBRIDS WITHIN THE GENUS SACCHARUM 313 
und in den an den Polen angelangten Chromosomen gewohnlich nur 
angedeutet ist. 
Solche Gebilde sind sehr charakteristisch fiir meiotische Teilungen 
wo Gemini und ungepaarte Chromosomen gleichzeitig auftreten und 
die letzteren im Aquator zu liegen kommen. In Drosera obovata waren 
sie nicht so deutlich zu sehen, weil hier die ungepaarten Chromosomen 
meistens ausserhalb des Aquators, oft in der Nahe der Pole gelagert 
waren.” 
Cytological investigations of hybrids between species with different 
chromosomes are also known of Oenothera-species. 
In this genus crosses have been made between species which possess 
in the diploid phase 14 chromosomes and the mutant Oenothera gigas 
with diploid 28 chromosomes, also between O. lata (diploid 15 chromo- 
somes) and O. gigas. . 
A great many hybrids obtained from these crosses proved to be 
sterile. A comparatively small number of fertile hybrids was obtained. 
Of the crosses between O. gigas and the other Oenothera-species de 
Vries 1) writes: „Die Bastardirungen gelingen in der Regel schwierig 
und die Hybriden sind fast ausnahmslos, entweder durchaus, oder doch 
nahezu steril”. 
Hybrids between O. Lamarckiana and O. gigas and such between O. 
lata and O. gigas have, with very different results, been investigated 
cytologically. à | 
GEERTS ?) states that in the prophase of the reduction division of 
these hybrids 7 gemini and 7 single chromosomes occur. To the forma- 
tion of the tetrad-nuclei generally chromosomes derived from the 
gemini only contribute, while the chromosomes which remained single 
in the heterotype division, form dwarfnuclei. In the case of an indivi- 
dual of the second generation of the cross O. gigas x O. Lamarckiana 
he found 14 chromosomes, pointing towards dissolution of the chromo- 
somes which failed to pair in diakinesis. 
Miss Lutz 8) however reaches other conclusions. Of 53 individuals of 
the second generation (49 of O. lata x O. gigas and 4 of O. Lamarckiana 
1) Huco DE Vries. Gruppenweise Artbildung. Berlin, Borntraeger, 1913, p. 
176. 5 
2) J. M. Grrrts. Cytologische Untersuchungen einiger Bastarde von Oeno- 
thera gigas. Ber. Deutsch. Bot. Gesellsch. Bd. 29. 1911, p. 160. 
3) ANNE M. Lutz. Triploid Mutants in Oenothera. Biol. CBI. XXXII, 1912. 
