ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 317 



siderably in closely related varieties of the same species. Cell-size 

 depends to some estent on the stage of development of the plant when 

 the organ was formed, the cells of organs of late development being 

 smaller than those in organs of early development. Difference in size 

 of any given organ is due to a difference in number of cells, not to cell- 

 size. 



The number of cells in each type of leaf is determined by 

 heredity, and the size of the organ is due to factors of periodicity 

 in growth, which determine, the rate and duration of cell-division. 



The cells of the lower epidermis of leaves have a characteristic length 

 and breadth, but in other regions their shape is modified by other factors 

 — e.g. presence of veins, stomata, etc. Differences in shapes of leaves 

 of the same plant are independent of the shape of the cells. The shape 

 of the leaf is due to factors of periodicity limiting the number and 

 direction of the cell-divisions in each type of leaf. S. G. 



Structure and Development. 

 Vegetative. 



The Use of Microscopical Characters in the Systematic Study 

 of the Higher Plants {Jo2fni. Q.M.G., April 1918, ser. 2, 13, 

 353-60). — In the Presidential Address to the Quekett Microscopical 

 Club for 1918, Dr. Rkndle points out the great use that may be made 

 of minute characters in the detection of species, instancing the valuable 

 work done on the microscopical structure of timber, especially in those 

 cases where only fragmentary material is available. Also that the 

 recognition of affinities among fossil plants is almost wholly based upon 

 microscopic characters. Plant hairs, pollen grains, and secretory glands 

 are also referred to. A. W. S. 



Reproductive. 



Effect of Foreign Pollination on Cycas Rumphil. — M. J. Le Goc 

 {Ann. Roij. Bot. Gard. Peradeniya, 1917, 6, 187-194). The author 

 describes his preliminary observations carried out in Ceylon. He finds 

 that while female plants of Cycas Rumphii are very abundant in Ceylon, 

 no male plant has been observed of late years. The dispersal of this 

 species of Cycas in Ceylon takes place by means of offshoots, and no 

 true seeds can be obtained. In the districts where no male plant of any 

 Cycad can be found, the ovules of C. Rumphii thrive only for a short 

 time, shrivel, decay, and fall off. But in localities where male cones 

 even of different genera occur, the ovules of C. Rumphii attain the size 

 of a fully mature seed ; but they contain no embryo, and consequently 

 do not germinate. On investigation it is found that foreign pollen 

 grains belonging to Encephalartos or Macrozamia have not only pollinated 

 C. Rumphii, but have produced male gametophytes. The full growth of 

 the ovules of C. Rnmphii must be attributed to the stimulus exercised 

 by these foreign male gametophytes. No true fertilization, however, 

 has been observed, or is likely to have taken place. Some minor points, 

 such as the effect of spores of fungi received inside the pollen chamber, 

 have also been discassed. A. B. R. 



