AGRICULTUEAL BOTANY. 29 



There was found to be a definite association between the species of weeds of 

 arable lands and the soil on which they grew. The determining factor is the 

 texture of the soil and not the geological formation from which it is derived, 

 except with soils overlying chalk. The crop has very little influence on weeds 

 except in the case of seed crops, which probably smother out a large number 

 of species which would normally occur. Certain weeds were found to be 

 definitely symptomatic of particular types of soil, though the majority of weeds 

 are not strictly circumscribed in this respect. 



Physiological aspects of fertilization and hybridization in ferns, W. D. 

 HovT (Hot. Guz., 4!) (1910), A o. J, pi,. S-'iO-SlO, Jig.s. 1.>).—Xn accownt is given 

 of an investigation into the hybridization and fertilization of ferns. The I'csults 

 of the author's experiments were negative, but they are considered as indicat- 

 ing the nonoccurrence of hybrids among ferns. 



The author studied the entrance of sperms into the archegonia, and the en- 

 trance was obtained in every combination of species tried. When the egg and 

 sperms were of the same species 37 fusions resulted, but when of different 

 species thoy failed to give a single fusion. The author believes from this evi- 

 dence that hybrids are not formed among this class of plants. 



Do ferns hybridize? It. C. I^nb^jict {Science, n. ser., S3 {1911), No. 8-'f2, pp. 

 254, 255). — In reviewing the above paper, the author criticizes the methods and 

 states that while it is quite true that experimental proof of the kind attempted 

 by Hoyt is lacking, yet no one has ever observed the development of a suspected 

 hybrid from before the period of fusion of the gametes. He claims that Hoyt's 

 arguments against fern hyl)ridity apitly with practically equal force to most 

 cases of accepted hybridity among fhowering plants and animals. 



It is said that there are a considerable number of i-eputed fern hybrids which 

 possess all the characters generally recognized as characteristic of hybrids, 

 and that the only reasonable explanation of their existence is to identify them 

 as has been the custom. 



The rules of Naudin and Mendel's law relative to the segregation of 

 hybrids, L. Blaringhem {Coinpt. Rend. Acad. Sci. [Paris], 152 {1911), No. 2, 

 pp. 100-102). — Attention is called to a memoir presented by Naudin to the 

 Academy of Sciences, Paris, in 1861, giving the results of S years' experiments 

 on the hybridization of Papaver, Mirabilis, Primula, Datura, Nicotiana, Petunia, 

 Digitalis, and Linaria, from which some generalizations were deduced. These 

 rules of Naudin are said by the author to be general principles, and the laws 

 of Mendel are considered by him as special applications. 



The two principles laid down by Naudin are as follows: (1) First genera- 

 tion hybrids of the same cross or reciprocal crosses will resemble each other 

 as much or nearly as much as different individuals of any recognized species; 

 (2) fertile hybrids and those fertilized among themselves will revert sooner 

 or later to the sijecific types from which they are derived. 



The author gives an account of the behavior of some crossbred barleys, the 

 segregation of which conforms to the above rules rather than to those of 

 Mendel. 



The mutation theory, II, H. de Vries, trans, by J. B. Farmer and A. D. 

 Darbishire {Chicago and London, 1910, vol. 2, pp. VIII+683, pis. 6, figs. 1^9). — 

 This volume completes the translation of the author's work on Die ^lutations 

 Theorie, the previous one having been noted elsewhere (E. S. R., 22, p. 625). 

 In it some of the data relating to the origin of horticultural varieties are col- 

 lated. This is followed by discussions of the origin of a number of eversport- 

 ing varieties and their relation to the author's theory, with concluding chapters 

 on the relation of the mutation theory to other branches of inquiry. 



