Varietäten, Descendenz, Hybriden. — Physiologie. 115 



Gregory, R. P., Abortive development of the pollen in 

 certain Sweet-peas {Lathynis odoratus). (Proc. Camb. Phil. 

 Soc. 1905. Xm. 3 p. 148-157). 



Sterility of the anthers, arising in certain of the offspring of a 

 hybrid between races of Lathyrus odoratus, was found to be a 

 Mendelian recessive character by Bateson. The author examined the 

 sporogenesis of the sterile plants as well as that of one of the normal 

 parent races. In the latter the spore-mother-cells developed accor- 

 ding to the usual method, a large nucleolus being present, and the 

 transference of chromatic material from the nucleolus to the nuclear 

 thread being observed. 



In the sterile plarits two forms of irregularity were seen , though 

 differing only in degree; in one chromosomes of a somewhat irregulär 

 appearance were formed, in the other abortion took place at an 

 earlier stage. Normal division of the pollen-mother-cell never took 

 place in these cases. The sterility was always confined to the anthers, 

 and the behaviour of the embryo-sac-mother-cells exactly resembled 

 that shown in the case of ordinary plants. R. H. Lock. 



Vries, H. de, Elementary Species in Agriculture. (Proc. 

 Am. Phil. Soc. XLV. 1906. p. 149—156). 



A critical examination of the evidence afforded the selection- 

 theory by the results of the agricultural plantbreeder. The methods 

 of German breeders are compared with those employed by Nilsso n 

 in Sweden and Hays in the United-State s. The author argues 

 that the slow improvement seen in the experiments of agriculturists 

 such as Rimpau is due to the fact that a number of elementary 

 and constant types were represented in their first selections and that 

 the slow improvement observed is due to the gradual elimination of 

 the less desirable of these. In the method of pedigree-cultures adopted 

 by Nilsso n and Hays and by careful students of heredity, the 

 less desirable elements of the Polymorphie population are recognized 

 much earlier — often in the first generation — and the improvement 

 is much more rapid, consisting, in fact, essentially in the selection 

 and pure propagation of the most desirable of the elementary species 

 already present. Harris. 



Beer, R., On the Development of the Spores of Helmin- 

 thostachys zeylanica. (Annais of Botany, Vol. XX, 1906. 

 p. 177-186. With two plates). 



In the first stage described the sporogenous cells have reached 

 their füll number and the tapetum consists of one to two layers. 

 Later on the tapetal walls break down, the cytoplasm increases in 

 amount and runs together and the nuclei are found in groups which 

 are partly formed by approximation of nuclei from several cells and 

 probably partly as a result of amitotic division: starch is found at 

 this time in the tapetal cytoplasm. The sporogenous cells now sepa- 

 rate into blocks; the middle lamella of the cellwalls becomes muci- 

 laginous and a secondary thickening layer remains round each cell. 

 The sporogenous cells divide into tetrads, but this does not take 

 place simultaneously; no disorganisation of the mother-cells occurs. 

 The tetrad wall is very thin and contains pectose; the young spore 

 wall is a new formation and is cuticularised. 



