ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 431 



tion appears to be one of aeration. In addition to an Anabxna-like 

 alga, at least three bacterial forms and the hyphae of a Rh I zob! urn-like 

 fungus were obtained from the cells of the tubercles, but none of these 

 organisms were identified. They suggest a symbiosis connected with 

 the supply of nitrogen to the host. 



Morphology of Gymnosperms.* — In the present volume Prof. J. M. 

 Coulter and Prof. C. J. Chamberlain supply us with a much needed 

 account of the present state of our knowledge respecting the external 

 morphology and the process of fertilisation in this class of vascular 

 plants, the interest of which has been so greatly increased since the 

 discovery of the ciliated spermatozoids, which are, however, as the 

 authors point out, not strictly homologous with the spermatozoids of 

 the pteridophyte, being morphologically sperm mother-cells rather than 

 sperms. The gymnosperms are classified under the four heads of 

 Cycadales, Gingkoales, Coniferales, and Gnetales, to which are added 

 chapters on Fossil Gymnosperms, Comparative Morphology, Phylogeny, 

 and Geographical Distribution. No attempt is made to describe the 

 internal anatomy. Although the outside title " Seed-plants," and the 

 inside title " Morphology of Spermatophytes," would imply a wider 

 scope, the present volume is confined to the treatment of Gymnosperms. 

 There is no index, a decided defect in the work. On the whole it is 

 admirable. 



j3. Physiology. 

 (1) Reproduction and Embryology. 



Basigamy, Acrogamy, and Mesogamy. f — Profs. R. Pirotta and 

 B. Longo propose a somewhat more definite use of the terms basigamy 

 and acrogamy than has hitherto been practised. By basigamy they 

 understand the process that has been observed in the Casuarineae, 

 Betulaceae, Corylus, &c, where the course of the pollen-tube is endotropic, 

 i.e. it makes its way through the tissue to the morphological base of the 

 ovule. Acrogamy is the ordinary process, where the course of the pollen- 

 tube is ectotropic, i.e. it creeps along the conducting tissue of the ovary 

 till it reaches the morphological apex of the ovule, and penetrates the 

 embryo-sac through the micropyle. In Ulmus, Cynomorium coccineum, 

 and the Cannabineae, an intermediate process has been observed, to 

 which they apply the term mesogamy. 



Parthenogenesis in Antennaria alpina. J — Dr. H. 0. Juel gives 

 further details of this phenomenon which he has already described, and 

 contrasts it with the perfectly normal process in A. dioica. In A. dioica, 

 besides the male and female forms, there are three other forms, one of 

 which is bisexual. In the production of the embryo-sac the first division 

 of the mother-cell is heterotypic (reduction in the number of chromo- 

 somes), while the second is homotypic. The development of the 

 oosphere into an embryo, and of the central nucleus to an endosperm, 

 take place only after impregnation. 



* ' Morphology of Spermatophytes,' New York, 1901, vii. and 1S9 pp. and 106 figs. 



t Atti r. Accad. Lincei, is. (1900) pp. 296-8. See Bot. Centralbl., Ixxxvi. 

 (1901) p. 93. 



% Handl. K. Svensk. Vetensk. Akad.. xxxiii. (1900) 59 pp.. 6 pis. and 5 figs. 

 See Bot, Ztg., lix. (1901) p. 131. Cf. this Journal, 1895, p. 557. 



