476 

 arranged metaphase similar to Ihe case described in Papaver hy- 

 brids by Ljungdahl (Sv. Bot. Tidskr. 1922). 



The tetrads in general present a normal appearance although 

 in some cases, as might be expected, five to seven cells are found. 

 In the laller sort two or three of the cells are of normal size and 

 the olhers quite small. The pollen is uniformally defective. When 

 immature the pollen grains are of good size but the chromatin is 

 obviously undergoing degeneration. Låter on shrinking and d.- 





•V 



■#':>-i? 





Fig. 2. Same hybrid as in fig. 1 d, "abnorma]^' condition 



(P. M. C.) following interkinesis and leading to the formation 



of diads. b, "normal" homotypic anaphases (P. M. C). 



c, E. M. C.-chalazal nucleus in anaphase. 



mlcropylar in interkinesis. 



stortion sets in, often with a simultaneous increase in size of the 

 tapetum which at times becomes so extensive as practically to 

 oblilerale the anther-sac. 



Tlie divisions in E. M. C. involve, in principle, the same pheno- 

 mena as have been described above for P. M. C. A niimber of 

 some general embryological interest have been observed and wdl 

 be treated of in a subsequent and more detailed report. As shown 

 in fig. 1 c the characleristic number of gemini and single chro- 

 mosomes appear in the heterotypic metaphase. Preparatory to 



