108 THE JOURNAL OF BOTANY 



known (not imagined) to be due to environment, really follows the 

 same laws. But in general, each factor of the fertilised egg's 

 constitution which controls the development of the mature indi- 

 vidual's visible characters, is quite independent of all the others. 

 Plants must therefore be said to be homo- or hetero-zygous in 

 respect of each factor separately, for they are rarely, if ever, capable 

 of being called homozygous plants. Individuals (and the races or 

 species they compose) in any species where self-fertilisation is not 

 absolute are almost certain to be heterozygous in respect of some 

 characters, which the working systematist usually then states to 

 be " of no importance " or " not good characters." Continuous self- 

 pollination following on a single chance cross-pollination inevitably 

 leads by the mathematical laws of chance to the gradual appear- 

 ance of increasingly liomozygous true breeding strains with every 

 possible combination of characters. Hence, doubtless, the " races " 

 of Senecio vulgaris, of Erophila verna, and so on. 



Those who wash to become conversant with the principles 

 involved cannot do better than obtain Doncaster's Heredity i7i the 

 Light of Becent Eesearch, one of the Cambridge (shilling) Manuals 

 of Science and Literature. More advanced works are R. C. 

 Punnett's Mejidelism, R. H. Lock's Variatiofi, Heredity 

 Evolution, and W. Bateson's Mendelian Principles of Heredity. 



NOTE ON PUCCINELLIA Pari. 



By the Editoe. 



In Rhodora, xviii, 1-23 (Jan. 1916) appears a paper on "The 

 Genus Puccinellia in Eastern North America," by M. L. Fernald 

 and C. A. Weatherby, which is of interest to British botanists, as 

 it proposes and apparently justifies the adoption of a generic 

 name which has not, I think, hitherto been taken up in British 

 books. The genus in Eastern North America includes ten species, 

 of which three are British — P. maritima Pari. (El. Ital. i, 370), 

 P. distans Pari. (op. cit. 367), and P. rupestris Eernald & 

 Weatherby, comb. nov. On this last the authors, having cited the 

 synonymy of the species — " Poa rupjestris With. Arr. Brit. PI. 

 ed. 3, ii. 146, t. 26 (1796). Poa procumhens Curtis, El. Lond., 

 fasc. vi. t. 11 (Exact date of publication not known but probably 

 later than Withering's species. See note below). Sclerochloa pro- 

 cumhens Beauv. Agrost. 98 (1812). S. riLpestris Britten & Rendle, 

 Journ. Bot. xlv. 107 (1907). Glyceriaptrocumhens Sm. Engl. El. i. 

 119 (1821). Festuca procumhens Kunth, Gram. i. 129 (1829). 

 Atropis procumhens Thurb. Bot. Cal. ii. 309 (1880) " — have an 

 interesting note : — " Britten & Rendle give excellent reasons for 

 concluding that Poa rupestris With, was published earlier than 

 P. procumhens Curtis : — see Journ. Bot. xlv. 107 (1907). In 

 addition to their reasoning it maybe noted that Withering, in his 

 original description (ed. 3) states merely that the plant was 



