AND SPECIES-HYBRIDS WITHIN THE GENUS SACCHARUM 321 
mutationen eingetreten sein. Aus der Tatsache, dass einige Spezies mit 
erhöhter Chromosomenzahl apogam oder apospor sind, hat man bisher 
den Schluss gezogen, dass die Vereinigung der Apogamie mit tetraploi- 
der Chromosomenzahl auf dem Vorhandensein kausaler Beziehungen 
zwischen beiden Erscheinungen beruhe. Es müssten demnach ganz 
ähnliche Beziehungen auch zwischen Chromosomenverdoppelung und 
Bastardierung sowie zwischen Chromosomenverdoppelung und Muta- 
tion existieren. Einer solchen Annahme gegenüber erscheint es wohl 
zweckmässiger, die Erhöhung der Chromosomenzahl nicht als Ursache, 
sondern als Begleiterscheinung von Apogamie, Mutation und Bas- . 
tardierung zu betrachten und die Frage zu prüfen, ob nicht in allen 
Fällen dieselbe oder ähnliche Ursachen dieselbe Folgeerscheinung 
auslösen.” | | 
In addition to the tetraploid hybrids, ERNST therefore will bring 
part of the apogamous plants to the group of hybrids with increased 
chromosomenumber. He moreover asks himself whether not, by the 
same or similar causes, increase of chromosomenumber has taken place 
among apogamous plants, tetraploid hybrids and mutants. 
As to the Saccharum-hybrids mentioned above, it seemed to me that 
they must have originated from a fertilisation in which a diploid num- 
ber of Saccharum officinarum-chromosomes met the haploid number 
of chromosomes of S. spontaneum. Consequently these hybrids would 
be triploid and, as they arose from gametes with different chromosome- 
numbers, I propose to call them, in accordance with ERNST's nomen- 
clature: hetero-triploid. Triploid hybrids, obtained by crossing diploid 
species with different chromosomenumbers were, up to the present 
moment, unknown. On the other hand, triploid Oenothera- mutants 
and hybrids, from parents with equal diploid numbers are known. So 
far one was of opinion, that these Oenothera-hybrids and mutants had 
to have been arisen by the union of a diploid with a haploid gamete. 
In the case of our Saccharum-hybrids such a thing certainly did not 
happen. On the supposition, that really the same or similar causes have 
resulted in the chromosome-increase of these Oenothera-mutants and 
of the Saccharum-hybrids, a supposition which is not certain, one now 
could imagine that the triploid Oenothera-mutants also have arisen 
from a union of haploid mutated gametes. 
Ernst deems doubling of the chromosome-number possible, both 
as a consequence of a union of diploid gametes and as a consequence 
Genetica V 21 
