578 Cytologie. — Descendenz u. Hybriden. — Morphologie. 



studied were found to be double or twin grains, i. e. they contain 

 two more or less completely organized gametophytes ; one of these 

 is usually smaller than the other, and lies crosswise in the position 

 usually occupied by the prothallial cells, and in fact the extra game- 

 tophyte might be mistaken for a multicellular prothallus. The writer 

 calls attention to the varying degree of reduction of the male game- 

 tophyte shown in the different groups of gymnosperms, and attri- 

 butes the reduction to gradual modification rather than to mutation. 



M. A. Chrvsler. 



BAThSON, W. and R. C. Pünnett, A Suggestion as to the nature 

 of the „walnut" comb in fowls. (Proc. Cambridge Phil. Soc. 

 XHI. 3. p. 165—168. 1905.) 



The Suggestion is to the following effect: Rose comb and pea 

 comb are regarded respectively as rose no-pea, and pea no-rose. 

 The two pairs of allelomorphs 1. rose and absence of rose, and 

 2. pea and absence of pea, are regarded as being concerned in the 

 cross. The simultaneous presence of rose and pea gives rise to the 

 appearance known as „walnut", and the further behaviour of the 

 offspring of the cross is of a simple Mendelian character. 



R. H. Lock. 



Butler, E. J., Thebearing ofMendeiism on the suscepti- 

 bility of wheat torust. (Journ. agric. Sc. I. 3. p. 361 

 —363. 1905.) 



The author points out in connection with Biffen's work on 

 the inheritance of rust-immunity in wheats, that different wheais 

 show different degrees of susceptibility to rust in different countries. 

 On the supposition of the presence and absence of the „latent 

 germ" he considers that Biffens experiments have no bearing upon 

 the question of the validity of Eriksson's Mycoplasm Hypothesis. 



R. H. Lock. 



Hurst, C. C, Conference on Hybridisation. (Journ. Roy. 

 Hort. Soc. XXIX. 4. p. 417—433. 1905.) 



Notes on abstracts of papers read before the second Inter- 

 national Conference on Hybridisation and Plant Breeding, and publi- 

 shed in the Memoirs of the Horticultural Society ot New York. 



R. H. Lock. 



Thwaites, E., Curiosities of Hybridisation. (Orchid Review. 

 Xlll. 156. p. 353—354. 1905.) 



Notes on the effectiveness of the pollen in different species, 

 and on the ripening of the fruits derived from various Grosses. 

 Attention is called to the fact that apparently perfect fruits may be 

 formed, which contain no good seeds. R. H. Lock. 



Griffsths, D., Abnormalities in the fruiting habits of 

 Opiintias. ("Torreya. VI. p. 57—63. 1906.) 



Opuntia Kleiniae occurs in two forms, in one of which the fruit 

 is proliferous, and sets no seed, in the other the non-proliferous 

 fruit oroduces fertile seed. Among otlier observations recorded in 



