812 A CYTOLOGICAL INVESTIGATION OF SOME SPIECES 
dwarf nuclei were formed because not all chromosomes entered into the 
daughter nuclei. While the number of chromosomes in the two nuclear 
plates of the homotype division could be different, their total number 
was always the same e. g. 30, so that no chromosomes were dissolved. 
In the homotype-division the chromosomes split longitudinally. Some 
of them occasionally do not enter the tetrad-nuclei, in which case they 
form daughternuclei. Fertile pollen never developed. The hybrid was 
also sterile in the female line, it is true that embryo’s were formed when 
the hybrid was crossed with D. longifolia but germinating seeds failed 
to make their apparance. 
ROSENBERG !) also investigated many apogamous and facultatively 
apogamous Hteracium-species cytologically, as well as the Hieracium- 
hybrids, obtained artificially by OSTENFELD 2). He could show that 
diploid and tetraploid species were present in the subgenus Pilosella 
in which apospory occurs, and triploid and tretraploid forms in the 
subgenus Archiertacium in which odapogamy occurs. ROSENBERG found 
9 to be the basal chromosomenumber of Hieracium. Hybrids between 
diploid and tetraploid species, followed, in the division of the PMC, the 
Drosera-scheme. 
ROSENBERG deems it probable that the species Hieracium excellens 
itself is ahybrid between species differing in chromosomenumber. The 
behaviour of the univalent chromosomes of H. excellens agrees quite 
with that of Saccharum officinarum. About it ROSENBERG says: 
„In der Metaphase treten 18 Gemini und 6 ungepaarte Chromosomen 
auf. Hier liegt also, meiner Ansicht nach, ein neues Beispiel von einer : 
nach dem Drosera obovata-Schema verlaufenden heterotypischen Tei- 
lung mit Gemini und ungepaarten Chromosomen vor, das wohl auf eine 
vorausgegangene Bastardierung hindeutet. Besonders deutlich zeigt 
sich dies in der Anaphase. Was am meisten auffällt, sind die paarig 
angeordneten, längs gespaltenen, kleineren Chromosomen im Aquator. 
Diese entsprechen ganz sicher den in der Metaphase auftretenden unge- 
paarten Chromosomen, die im Äquator eine Längsspaltung ausführen, 
welche normalerweise in dem nächsten Teilungsschritt folgen sollte 
1) O. ROSENBERG. Die Reduktionsteilung und ihre Degeneration in Hiera- 
cium. Svensk Bot. Tidskrift. Bd. 11. 1917, p. 145. 
*) C. H. OSTENFELD. Further Studies on the Apogamy and Hybridization 
of the Hieracia. Zeitschrift für ind. Abst. und Vererbungslehre. Bd. III, 1910. 
p 239. 
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