ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 43 



enzyme-formation. The result is the production of a great variety 

 of nutritive material, partly the direct product of enzyme-action, partly 

 produced by the secretory activity of the protoplasm, and partly by the 

 interaction of the products of the first two agents. Among the sub- 

 stances formed are two varieties of sugar, lecithin, fatty acids and the 

 products of their oxidation, proteids and the products of their digestion, 

 including various crystalline nitrogenous bodies, amino- and amido- 

 compounds. The embryo absorbs from this mass of nutritive material, 

 in which it is plunged, by means of the delicate epidermis of its 

 cotyledons, probably selectively, what it needs for growth. 



Analyses of the cotyledons showed them to contain a varying 

 quantity of lecithin, amounting in some cases to 1'86 p.c. of their dry 

 weight. Both the sugars can be detected in them ; the relative 

 amounts varied, but cane-sugar is usually present in largest quantity. 

 The reaction of the sap is acid, traces of phosphoric acid being mixed 

 with an organic acid. The transport of nutritive materials to the 

 embryo seems similar to their transport in the tissue of the endosperm. 

 Probably in both cases the presence of protoplasmic threads in the 

 various cell-walls plays an important part in the matter ; at any rate, 

 this agency seems necessary to explain the transport of lecithin to the 

 embryo. Thus the renewed metabolism in the endosperm-cells supplies 

 a mass of nutritive material on which both the endosperm-cells and the 

 young embryo feed, and there seems no particular difference in the 

 manner in which they are severally nourished. 



irritability- 

 Irritability in Algae.* — G. J. Pierce and Flora A. Randolph have 

 studied the circumstances attending the attachment and germination of 

 the zoospores of fresh-water and marine algge. The germination of the 

 zoospores of sessile algae is apparently induced primarily by interference 

 with their locomotion. The nature of the attachment formed by the 

 germinating zoospores depends upon the roughness of the surface of the 

 object with which they come into contact. Upon very smooth surfaces, 

 such as the surface of clean water and clean wet gelatin, the spores 

 form either only the shortest, most rudimentary holdfasts, or merely 

 rhizoids ; whereas on relatively rough surfaces the holdfasts are large, 

 and conform in their lobing to the contour of the surface. Even 

 ordinarily floating algas may sometimes be induced to form rhizoids or 

 other organs of attachment if brought into contact with sufficiently 

 rough surfaces. The discharge of the spores or gametes of Dictyopteris, 

 Diciyota, and Cystoseira is strongly influenced by light, being much 

 more rapid within a few hours after exposure to light than before, or 

 than in continuous darkness. Hence the time of the discharge as well 

 as the rate is strongly influenced by light, and a periodicity is established 

 which follows approximately that of daylight and darkness. The 

 authors find, as shown by Winkler in Cystoseira, that the direction in 

 which the light falls determines the place of the first division in the 

 germinating spores of Cystoseira, Dictyopteris, and Dictyota, the new 



* Bot. Gazette, xl. (1905) pp. 321-50 (27 figs, in text.) 



