76 MORPHOLOGY, ETC., VASC. PLANTS [Bot. Absts., Vol. V, 



of which probably belonged to the Cord ait ales, form a series illustrating a general tendency, 

 a continuation of which has resulted in the production of the type of seed found in Taxus, as 

 well as in Torn an and Cephalotaxus. This tendency may be summarized as follows: The 

 point of origin of the "outer" system of vascular strands shifts nearer and nearer the subnu- 

 cellar pad of tracheids which gives rise to the "inner" system. During this process the bun- 

 dles of the outer system cut through the "stone." The canals through the stone then move 

 forward toward the micropyle so that for an increasing distance the bundles come to lie in- 

 side the stone. At the culmination of the process when they lie entirely within the stone the 

 condition found in Taxus is reached. In this genus the "inner" system of bundles has dis- 

 appeared. The seeds of Torreya and Cephalotaxus are derived from the same source by a 

 modification of the same tendency. On the basis of this theory these three genera are the 

 nearest existing relatives — apart from Ginkgo— of the Cordaitales and like Ginkgo have been 

 derived directly from the Cordaitales. It is proposed to place them in a separate group 

 the Taxales, distinct from Coniferales and nearer Ginkgo. — W. P. Thompson. 



575. St. John, Harold. The genus Elodea in New England. Rhodora 22 : 17-29. 1920. 

 —See Bot. Absts. 5, Entry 451. 



576. Salisbury, E. J. Variation in Anemone apennina, L., and Clematis vitalba, L., with 

 special reference to trimery and abortion. Ann. Botany 34: 107-116. 9 fig. 1920. — This 

 paper furnishes additional data supporting the author's previously published views concern- 

 ing the essential trimery of the Ranunculaceous flower and the causes of variation in the 

 numbers of the constituent parts. Curves are given showing the variation in the number of 

 stamens, carpels, and perianth parts in a large number of flowers of the species studied. The 

 curves show marked periodicity, the crests occurring at multiples of three. In more than 

 half the flowers of Anemone apennina the stamens and carpels are in multiples of three. Evi- 

 dence is given to show that congenital fission is the chief cause of variation in number, though 

 transformation of stamens into perianth parts was also observed. — W. P. Thompson. 



577. Schaffner, John H. Dieciousness in Thalictrum dasycarpum. Ohio Jour. Sci. 

 20: 25-34. 1919. — Intermediate forms between extremes of staminateness and carpellateness 

 are described. Great diversity of sexual expression is found on different branches of the same 

 inflorescence. It is concluded that maleness or femaleness is determined by the physiological 

 state at the inception of the sporophylls; or that if sex has been determined earlier, it is later 

 reversed. A general survey of the origin and nature of dieciousness in sporophytes is given, 

 showing evolutionary gradations from the bisporangiate to the monosporangiate condition 

 in various groups. — H. D. Hooker, Jr. 



578. Seward, A. C. [Rev. of: Chamberlain, C. J. The living cycads. Univ. Chicago 

 Science Ser. 172 p. 91 fig. Univ. Chicago Press: Chicago, 1919.] New Phytol. 18: 262. 

 1919. 



579. Small, James. The origin and development of the Compositae. Miscellaneous 

 topics. New Phytol. 18: 129-176. Fig. 64-78. 1919.— See Bot. Absts. 5, Entry 720. 



5S0. Small, James. The origin and development of the Compositae. General conclu- 

 sions. New Phytol. 18: 201-231. Fig. 79. 1919. 



581. Soueurs, R. Embryogenie des Polygonacees. Developpement de l'embryon chez 

 le Polygonum Persicaria L. [Development of the embryo of Polygonum persicaria L.] Compt. 

 Rend. Acad. Sci. Paris 168: 791-793. 8 fig. 1919. — The two-celled proembryo of Polygonum 

 persicaria L. gives rise, by a series of transverse divisions, to six layers of cells, the upper two 

 being derived from the apical cell and the lower four from the basal cell. The two layers pro- 

 duced from the apical cell give rise respectively to the cotyledons, as in the Ranunculaceae 

 and Cruciferae, and to the upper portion of the hypocotyl. In the Ranunculaceae and Cru- 

 ciferae the corresponding layer gives rise to the complete hypocotyl. The four layers derived 

 from the basal cell of the two-celled proembryo give rise respectively to (1) the lower portion 

 of the hypocotyl; (2) the root cap; and (3) and (4) a rudimentary suspensor. — F. B. Wann. 



