ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 273 



as in Vallisneria and Hydrilla, or below the surface, like the absence 

 of extinc, as in Naias and Ceratopliyllum. 



The author enters into further details respecting the mode of life 

 and variability of water-plants, their hibernation, their vegetative 

 multiplication, the structui-e of the flowers, the dissemination of the 

 seeds, their germination, and geographical distribution. 



Pollen - tubes.* — M. C. Degagny finds that the " cellulose 

 stoppers " which obstruct the pollen-tube do not consist of cellulose. 

 By the use of methyl-blue, which stains cellulose, the membrane is 

 not coloured, but the protoplasm of the " deposit " is stained ; this 

 indicates that this is analogous to, but not identical with, the callus of 

 sieve-tubes ; for whilst the latter is not stained by chlor-iodide of 

 zinc, the former is. He concludes that these deposits are proto- 

 plasm, richer in carbo-hydrates than is the callus, in which the 

 nitrogenous substances prevent the staining by means of this reagent. 

 Assimilation ends in the formation of a large quantity of uncoloured 

 protoplasm, the degradation of which is so much the more rapid in 

 proportion as the nitrogen reserve materials have not time to be 

 formed in sufficient quantity. The degradation is not complete, as 

 in ordinary cellulose secretions ; in fact, these new reactions show 

 that the nitrogen is not totally eliminated. These are phenomena 

 special to the male cell or pollen-tube and to the increase of proto^ 

 plasm, which is the active element of fertilization. 



White-seeded Variety of the Honey-locust. t — Mr. T. Meehan, 

 referring to seeds of an old specimen of Gleditschia triacanthos, which 

 were white instead of the ordinary olive-brown colour, and which 

 showed other differences from the ordinary variety, said that this was 

 the only known instance of the species producing white seeds. He 

 suggested that environment was not so great a factor in producing 

 variations as it was usually considered to be, and is inclined to attri- 

 bute the variation to the " plant's own innate power to change," since 

 it is difficult to see how this one tree, out of several growing in the 

 neighbourhood and under exactly the same conditions of climate and 

 soil, could be influenced by its environment. Cross-fertilization often 

 produced great changes in the colour of seeds of Indian corn. 



Germinative Power of Seeds after exclusion of Air and Drying 

 at High Temperatures.^ — Experiments carried on by Herr Wilhelm 

 as to the povper of germination of seeds dried and hermetically sealed, 

 gave the following results, with winter wheat, rye, oats, and linseed. 

 Exclusion from air enables the seed to retain its vitality longer than 

 when air has access to it ; two hours' heating at 50° C. removes water 

 and preserves the seed well ; when heated to a higher temperature 

 the seeds germinate more slowly. Seeds which have been artificially 

 dried, when subsequently moistened, absorb more water than they 

 would otherwise have done. 



* Comptes Rendus, cii. (1886) pp. 230-1. 

 t Proc. Acad. Nat, Sci. Philad., 1885, pp. 404-5. 



+ Jourii, Chem. Soc. Lond., 1. (1886) p. 171, from Died. Central., 1885, 

 pp. 611-3. 



Ser. 2.— Vol. VI. T 



