262 GENETICS [BoT. Absts., Vol. VII, 



1812. MacLeod, J. The quantitative method in biology. 15 X 23 cm., v + 228 p., 27 fig. 

 Longmans, Green & Co. : New York, 1919. — The thesis taken by the author is that all classi- 

 fied groups, species, etc.; all variation, Mendelian or otherwise; in fact all biological phe- 

 nomena, should be measured and reduced to constants, similar to those of the physicist. 

 These constants will then form the basis of exact description necessary to further biological 

 progress. — Up to the present, the great variation of biological phenomena has barred the 

 application of this method. Preliminary study of the specimen reveals certain primordia, 

 or simple elementary properties of characters, which are to be measured in order to find the 

 constants mentioned above. The primordia for each subject are to be determined independ- 

 ently by preliminary study. — The rest of the book is given over to expansion and illustra- 

 tion of this thesis. Discussion of quantitative methods is merely a side issue, only the 

 simplest of them being used for illustration purposes. [See also Bot. Absts. 4, Entries 758, 

 352S.]— John W. Gowen. 



1813. Matthews, J. R. Hybridism and classification in the genus Rosa. New Phytol. 

 19: 153-171. July-Oct., 1920. — Classification of roses is complicated by natural hybridiza- 

 tion, for which there is abundant opportunity. A number of Rosa species are now acknowl- 

 edged hybrids due to their intermediateness. Others are suggested by sterility, on basis of 

 Jeffrey's "crypthybrid" principle. Author classifies genus in 5 sections and 18 groups. 

 Members of each group differ in only a few unit characters. For each group author uses some 

 or all of the following unit characters, and shows that majority of combinations theoretically 

 possible have already been recognized and usually given specific names: hairy vs. glabrous 

 leaflets (Hh); biserrate vs. not biserrate (Bb); presence vs. absence of foliar glands (Gg); 

 hispid vs. smooth peduncles (<Ss). Believes morphological methods alone insufficient for solu- 

 tion of problems involved; emphasizes need of breeding work, upon which new classification 

 should be based, involving return "to the Linnean conception of the species, denoting its vari- 

 ous combinations by some purely symbolical method." — 'Merle C. Coulter. 



1814. Merriman, Mabel L. Studies in the conjugation of Spirogyra temata. Bull. Tor- 

 rey Bot. Club 47: 9-20. 3 fig. January, 1920. — Records differences in form and volume of 

 male and female gametangia in S. ternata. Suggests that differences may be due to dif- 

 ferences in metabolism. — E. N. Transeau. 



1815. O'Neal, C. E. Microsporogenesis in Datura stramonium. Bull. Torrey Bot. 

 Club 47: 231-241. 2 pi. 1920.— The maturation stages are found in anthers 2 to 4 mm. long. 

 The diameter of the pollen-mother-cells in the resting stage is about 25 microns. Synizesis 

 is figured. Doubleness of the spireme thread was visible before its segmentation. Twelve 

 bivalents were counted, and no differences in shape or size were made out. In the spindles 

 of the second division the chromosomes are evenly spaced, and have "an almost diagram- 

 matic appearance." [See Bot. Absts. 6, Entry 1001.]— John Belling. 



1816. Orban, G. Untersuchungen iiber die Sexualitat von Phycomyces nitens. [Sexu- 

 ality of Phycomyces nitens.] Beih. Bot. Centralbl. 36: 1-59. 2 pi., 20 fig. 1919.— Author 

 attempts to make a more thorough investigation of processes of sexual reproduction already 

 known in Phycomyces nitens. The sexes are distinguished by secondary sexual characters 

 which are constant for all (+) and ( — ) races, even for those obtained by germination of 

 zygospores. Cultural conditions influencing strength of zygosporic line between hetero- 

 thallic races are investigated. Homothallic mycelia are studied in detail in regard to pro- 

 duction of pseudophores, formation of zygospores entirely from homothallic filaments or 

 jointly from homothallic and heterothallic filaments, formation of azygospores and sporangia 

 and changes in sexual reaction from homothallic to heterothallic. On certain substrata 

 pseudophores are formed at line of contact between (+) and ( — ) races. — A. F. Blakeslee, 



1817. Patterson, J. T. Polyembryony and sex. Jour. Heredity 10 : 344^352. Fig. 4-5. 

 1919. — The author gives data of the numbers of male, female, and mixed broods of three species 

 of parasitic hymenoptera: Copidosoma gelechiae, Paracopidosomopsis floridanus, and Platy- 



