Varietäten, Descendenz, Hybriden. 235 



in F, breed true: some susceptible plants breed true, others give 

 otfspring showing segregation. There is much Variation in the degree 

 of susceptibility: this is partly hereditary, but may be greatly affec- 

 ted by changes in metabolism due to manuring etc. 



In the case of Claviceps piirpiirea, it appears that crosses between 

 two reputedly immune parents may give a susceptible F^, (though 

 this does not occur in every case). It is suggested that two comple- 

 mentary factors are necessary to produce susceptibility to Claviceps 

 in W heat. 



It is shown that there is no good evidence of the failurc of 

 immunity in cultivation. R. H. Compton (Cambridge,/. 



Digby, L., The Cytology of Prinmla kewensis and ofother 

 related P. hybrids. (Ann. Bot. XXVI. 102. p. 357— 388. pl. 41-44. 

 2 textfig. 1912.) 



The sterile hybrid P. kewensis, has, like both of its parents P. 

 Jloribunda and P. verticiUata , the diploid number of 18 chromoso- 

 mes. This stock, propagated vegetatively, produced thrum-eyed 

 flowers: but a Single pin-eyed flower appeared in 1905, by crossing 

 this with thrum pollen, seed was set, and yielded fertile offspring, 

 (referred to as the seedling P. kewensis). This new form, as well as 

 another produced by selection from it, viz. P. kewensis farinosa, 

 (which also arose from the cross P. verticiUata X P- floribunda 

 isabellina) has 36 diploid chromosomes. On the other hand, P. flori- 

 bunda isabellina crossed by the seedling P. kewensis yields a hybrid 

 with onl}' 18 softiatic chromosomes. 



In P. floribunda and the seedling P. ke^iensis there is no second 

 synaptic contraction, but this is well shown in P. verticiUata and 

 indications of it are found in the sterile P. kewensis. Synapsis is 

 telosynaptic, a continuous Univalent spireme being formed: from 

 this a parasynaptic union is produced by looping. Protrusions of 

 chromatin from a nucleus into the adjacent cell are sometimes 

 found in the „open spireme" stage of P. kewensis (type). Compari- 

 sons are drawn with nuclear phenomena in species of Oenothera 



R. H. Compton (Cambridge). 



Wheldale, M., The chemical d ifferen tiation of species. 

 (Bioch. Journ. V. p. 445—456. 1911.) 



The author draws attention to the fact that plant form is an 

 expression of its chemical Constitution the origin of a variety, the- 

 refore must be regarded as a fundamental change of chemical 

 nature. 



An account is given of the distribution of a few of the various 

 classes of organic Compounds found in plants in order to show, as 

 far as possible 1) that many Compounds are peculiar to certain 

 species, genera or natural Orders; 2; that allied Compounds of 

 restricted distribution are offen found in the species or genus. 



Miss Wheldale suggests the lines along which investigations 

 might be carried out. G. Paine. 



Zacharias. E., üeber das teilweise Un fruchtbar werden der 



