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



interspecific crosses between T. crepuscularia and T. bistortata a nondescript series of inter- 

 grades results in F2 in respect to this same character. Thus, what behaves as a single unit 

 character in one cross shows itself highly inconstant in another, owing, author believes, to 

 "contamination of the gametes." This difference is intunately connected with inability of 

 chromosomes in wider crosses to play their normal parts, owing to "incompatibility." If 

 genetic factors may thus be modified by hybridization, possibility of their modification by 

 other agents seems not excluded. — F. B. Sumner. 



895. Hartman, Carl G. The free-martin and its reciprocal: Opossum, man, dog. Sci- 

 ence 52: 46&-471. Nov. 12, 1920.— The author describes very briefly an intersexual opossum: 

 "externally, normal penis, empty scrotum, small malformed pouch, head rather like that 

 of a female; internally, reproductive organs distinctly of the female type, infantile in devel- 

 opment, consisting of vaginal canals, uteri. Fallopian tubes, and small round bodies in the 

 situation of the ovaries." These bodies consisted of a thin albuginea, and a mass of tubules 

 of uniform size consisting apparently of Sertoli cells only.— The history of the specimen was 

 not known. The author, arguing from analogy, interprets it as a "reciprocal free-martin"; 

 i.e., a sex-intergrade zygotically male, which in its ontogeny develops female characters. 

 He points out the opportunity that exists in the crowded pregnant uterus of the opossum 

 for anastomosis of foetal circulations, which might account for such a condition if the female 

 of a fused pair developed sex hormones in advance of the male. Fusion of placentae has 

 been observed in dog embryos by Evans; and Eschricht describes a case of fused placentae 

 in a case of two-sexed human twins in which the male was similar to the opossum described 

 above, and the female was normal. The principles involved are considered to throw much 

 light on the entire subject of hermaphroditism in mammals. — Frank R. Lillie. 



896. Hendrickson, H. C. . The selection of seed corn in Porto Rico. Porto Rico Agric. 

 Exp. Sta. Circ. 18. 22 p., 7 fig. Sept. 2, 1920.— Intended as a practical guide to farmers. 

 Contains no new methods. [See also Bot. Absts 7, Entry 614.]— .E. E. Barker. 



897. Henry, A. Sports and varieties of trees : A new sport of the lime tree. Gard. Chron. 

 68: 180. Oct. 9, 1920.— A large secondary branch of Tilia vulgaris bore leaves which were 

 white with rare patches of green. The white leaves yielded to alcohol less than one-twen- 

 tieth of the chlorophyll found in normal leaves. — John Belling. 



898. Herlant, Maurice. L'acide carbonique comme agent de parthenogenese experi- 

 mentale chez I'^oursin (Paracentrotus). [Carbonic acid as an agent of experimental partheno- 

 genesis in the sea-urchin (Paracentrotus).] Compt. Rend. Soc. Biol. 83: 188-190. 1920.— 

 Delage found eggs of sea-urchin, unlike those of starfish, were not activated by exposure for 

 an hour to sea water saturated with carbon dioxide. Author obtains development in sea- 

 urchin egg by exposing it to carbon dioxide one and one-half to two minutes, returning to sea 

 water for 20 to 30 minutes, then putting into hypertonic solution equal time. He conceives 

 first treatment to activate egg as whole, second to produce asters by which division is 

 effected. — A. Franklin Shull. 



899. Hovasse, R. Le nombre des chromosomes chez les tetards parthenogenetiques de 

 grenouille. [The number of chromosomes in parthenogenetic tadpoles of the frog.] Compt. 

 Rend. Acad. Sci. Paris 170: 1211-1216. May, 1920. 



900. Hume, A. N., M. Champlin, and M. Fowlds. The influence of length of wheat 

 heads on resulting crops. South Dakota Agric. Sta. Bull. 187: 139-158. 1919.— Twelve hun- 

 dred plants of Bluestem wheat were grown under nearly identical conditions. From these, 

 two hundred and sixty were selected, having as nearly as possible the same number of stools 

 —the reason for this selection being that stooling differences should be eliminated as a factor, 

 if possible. The length of the central head of each plant was measured. From each of those 

 heads twenty seeds were selected at random and were planted at uniform spaces in individual 

 head-rows. The yield of grain from each row was recorded and correlated with the length 



