604 SUMMARY OF CURRENT RESEARCHES RELATING TO 



elements in the non-irrigated forms of the Egyptian-Arabian deserts as 

 given by Volkens. The irrigated plants have a greater absolute trans- 

 piration, and form each year a larger amount of wood than non-irrigated 

 plants of the same age ; but the composition of the wood is different in 

 the two cases. The irrigated plants form a relatively large amount of 

 non-conductive tissue each year, while the reverse is true of the non- 

 irrigated plants. Hence in stems of equal diameter, but not of the same 

 age, the non-irrigated and older stems have more vessels than the 

 irrigated and younger. The ducts were usually or frequently of greater 

 diameter in non-irrigated stems. 



Reproductive. 



Megaspore Membrane in Gymnosperms.* — R. B. Thomson has 

 investigated the coat of the megaspore in Gymnosperms. It is present 

 in all except the Taxeae, where it is almost or entirely absent. It con- 

 sists of two layers, the outer suberised, the inner of a composite character 

 being suberised in its outer portion and containing cellulose associated 

 with a pectin-like substance in its inner portion. Briefly, it resembles 

 the microspore coat in structure and composition. In the Araucarieas 

 the suberised outer layer is absent. The forms with the usual type of 

 membrane have a more or less well-developed tapetum, derived from the 

 sporogenous tissue, which is quite distinct from that derived from 

 nucellar tissue. From the relative development of the megaspore coat 

 and of the tapetum, the author concludes that the Abieteas are the most 

 ancient groups of Coniferales, and the Taxeaa the most recent ; that the 

 Taxodieas and Podocarpeas are complex, and include both ancient and 

 recent forms ; and that the Cupressese occupy an intermediate position. 



Development in Ovule and Seed of Anona.f — N. Roncati has 

 studied the gametophyte and embryology in Anona Cherimolia. He 

 finds a row of four megaspores and a considerable amount of parietal 

 tissue. From the lowest megaspore is formed a narrow and much 

 elongated embryo-sac, with apparently ephemeral antipodal cells. In the 

 formation of endosperm a series of walls appears across the narrow embryo- 

 sac, which becomes divided into a linear series of five or six large-chambers, 

 which subsequently become filled with tissue. The embryo has no 

 suspensor, but arises from a globular mass of cells. The rumination of 

 the seed is explained by the invasion of the perisperm by infoldings, 

 chiefly of the inner integument. The author gives the name " reserve 

 idioblasts " to masses of nutritive material found in abundance in cells 

 along the convolutions of the rumination, and thought to supply nutri- 

 tion to the embryo after the digestion of the endosperm. 



Points in the Life-History of Apocynum.J— T. C. Frye and E. B. 

 Blodgett have studied the minute morphology of the flower and the 



* Univ. Toronto Biol. Series No. 4 (1905) 64 pp., 5 pis. See also Bot. Gazette, 

 xxxix. (1905) p. 429. 



t Atti Acad. Gioenia Sci. Nat. Catania, xviii., Mem. 2 (1904) 26 pp., 1 pi. See 

 also Bot. Gazette, xxxix. (1905) p. 430. 



X Bot. Gazette, xl. (1905) pp. 49-53 (1 pi.). 



