304 BOTANICAL GAZETTE [may 



(J 



ASBURGER 66), TJialictrum puYpurascens 



lum Ula (LoTSY 40), several forms of Taraxacum (Raunkiaer 57; 

 MuRBECK 47; JuEL 32,33), a number of species of Hieracium 



(OSTENFELD 50, 51; MuRBECK 47; ROSENBERG 59), and Wik- 



stroemia indica (Winkler 75, 76). Among these contributions 

 those of Juel, Murbeck, Overton, Strasburger, Winkler, and 

 Rosenberg present some very interesting cytological data. 



Juel (30, 31) made a comparative study of the parthenogenetic 

 Antennaria and the normally fertiUzed A. dioica. In the latter a 

 tetrad is formed from a megaspore mother cell, with the usual reduction 

 of chromosomes, and the embryo sac is developed from one of the 

 megaspores. There is a typical synapsis preceding a heterotypic 

 mitosis, and the embryo sac is normal. The reduced number of 

 chromosomes is 12-14 in the pollen mother cell and 20-24 in the 



In the parthenogenetic Antennaria alpina, not only is 

 the tetrad suppressed, but there is no trace of heterotypic and homo- 

 typic mitosis in the embryo sac. The number of chromosomes is 

 40-50 in the embryo sac and 45-50 in the integument. There is thus 

 no reduction of the chromosomes during the formation of the embryo 



integument. 



sacj and the egg retains the sporophytic number. 



Mu 



chief 



attention being paid to the parthenogenetic A. alpina. In the 

 parthenogenetic species of Eualchemilla, he found that the embryo 

 sac always developed from one megaspore of the tetrad produced 

 from the megaspore mother cell through two successive mitoses, in 

 which there seemed to be no evidence of a reduction of chromosomes. 

 The number of chromosomes in these divisions is approximately 32-48, 

 and this number is retained in the egg nucleus and the other nuclei of 

 the embryo sac. He reports that the embryo of A . sericala is produced 

 from a syncrgid. In the normal species A. arvensis, belonging to the 

 section Aphanes, he finds in the pollen mother cell 16 chromosomes 

 the reduced number. Two years later, Murbeck (47) in a short paper 

 announced that embryos in Taraxacum viilgare Raunk. and speciosunt 

 Raunk. and Hieracium grandidens, serratijrons, and subsp. crispa- 

 turn develop from flowers whose stamens have been removed, but 

 he did not make any cytological studies. Juel (32 , 33) discovered a 



