296 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including tlie Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including- Cell-contents. 



Cytology of Primula kewensis and Related Hybrids.* — L. Digby 

 contributes an interesting paper dealing with the cytology of Primula 

 keirensis. The sterile hybrid, obtained by crossing F. florihunda with 

 the pollen of P, vertirillata, possessed the same number of chromosomes 

 as the parents, i.e. 9 and 9x2. A fertile plant produced some years 

 later is found to have doubled the number of chromosomes, and this 

 number also appears in the variety P. keiuensls farinosa. On the other 

 hand, P. floribunda var. isabeUina crossed witli the fertile P. keicensis has 

 the reduced number. The prophases of the premeiotic divisions show 

 a stringing together of homogeneous beads of chromatin, which gradually 

 condense to form chromosomes. In P. fioribunda and in the fertile 

 hybrid there is no second contraction ; in P. verticillata contraction 

 occurs, while in the sterile hybrid there is amalgamation but no definite 

 contraction. In the heterotype division of the fertile hybrid a large 

 quadrivalent chromosome is formed. The homotype division is normal. 

 The author emphasizes the similarity to the behaviour of the QiJno- 

 theras, and points out that the doubling of the number of chromosomes, 

 which accompanies the appearance of fertility in the hybrid, appears to 

 ])c due to longitudinal fission : and that the reduced number found in 

 the hybrid obtained by crossing P. floribunda var. isabelUna with the 

 fertile P. kewensis is probaljly due to elimination as a result of disinte- 

 ofration, similar to that found in the CEnotlieras. 



Chromosomes in Polypodium.t — H. cle Litardiere contributes a 

 note upon the heterotypic chromosomes in Polyfodium vidgare, in which 

 he states that the fine threads derived from the nuclear network arrange 

 themselves in pairs and form a thick spireme. Ultimately they separate, 

 thicken, and shorten in order to form the two-branched chromosomes 

 characteristic of diakinesis. This statement confirms the descriptions 

 given by Gregoire, Cardiff, and Yamanouchi for several other ferns, and 

 is opposed to those given l)y Farmer, Moore, and Strasburger. It seems 

 probable to the author that the differences might be reconciled if the 

 post-spireme stages were studied in more detail. ' 



* Ann. Bot., xxvi. (1912) pp. 357-88 (4 pis. and 2 figs.), 

 t Comptes Rendus, civ. (1912) pp. 1023-6. 



