— 168 - 



then it seems to me probable that the opinion, that the apogamy 

 has originally begun as apospory simultaneously with a reduction 

 division of the embryo sac mothercell, is well founded. 



Strasburger in his work on Alchemilla (27) has called atten- 

 tion to the fact that polymorphous apogamic genera are charac- 

 terised by a great number of chromosomes. He points out, however, 

 that on one side several polymorphous genera have only a few 

 chromosomes, for instance Rosa, on the other side that in Tha- 

 lictrum purpurascens, which is also apogamic, there are only M 

 chromosomes. 



In Bieracium there is a great variation as regards the number 

 of chromosomes, and it is remarkable that the greatest number is 

 to be found in the apogamic forms. It seems to me that this fact 

 lies in connection with the apogamy, not the number itself, but 

 the fact that it is a double number. F. i. the Alchemilla species of the 

 group Aphanes, which are sexual, show the number 32, whilst the 

 apogamic Eualchemilla species show the number 64 in the somatic 

 cells. In Hieracium auricula there are 18 chromosomes and in H. 

 excellens 34. Perhaps this doubling of the number of chromosomes 

 is caused by a longitudinal division of the chromosomes without 

 nucleus division. I hope a further investigation of other apogamic 

 species will enable us to get more light upon this important point. 



Literature. 



1. Allen, Ch. E., Nuclear division in the pollen mother-cells of Lilium canadense. 



Ann. of Bo'c, XIX. 1905. 



2. Chamberlain, C. J., The embryo sac of Aster Novae-Angliae. Bot. Gaz., XX, 



1895. 



3. Hacker, V., Ueber das Schicksal der elterlichen und grosselterlichen Kernan- 



teile. Jena. Zeitschr. Nat. Bd. 37. 1902. 



4. — ■ — , Bastardirung und Geschlechtszellenbildung. Zool. Jahrb. Suppl. VII. 



Jena 1904. 



5. Juel, H. 0., Vergleichende Untersuchungen über typische und parthenogene- 



tische Fortpflanzung bei der Gattung Antennaria. Svenska Vet. Ak. 



Handl. XXXIII, 1900. 

 (5. - , Die Tetradenteilung in der Samenanlage von Taraxacum. Arkiv f. 



Bot. II, Stockholm 1904. 

 7. , Die Tetradenteilungen bei Taraxacum und anderen Cichorieen. 



Svenska Vet. Ak. Handl. XXXIX, 1905. 



