270 SUMMARY OF CURRENT RESEARCHES RELATINQ TO 



the spur, and take no part in the fertilization of the ovules, which is effected 

 only by long-styled bees. 



The author points out the great difference in structure between the 

 proboscis of a humble-bee and that of a butterily, the former being able to 

 turn the tip about in all directions, and thus obtain the honey from a spur 

 even when its apex points upwards, which is not the case with Lepidoptera. 



Fertilization of Cactacege.* — In opposition to the assertion of Krutt- 

 schnitt,! M. L. Guignard states, from observations on several species of 

 Cereus, that fertilization is effected in the ordinary way by the pollen-tubes 

 penetrating the conducting tissue of the style and entering the micropyle 

 of the ovules. The structure of the ovary and ovules presents, however, 

 several peculiarities. The very long funicles branch, in C. tortuosus, into 

 as many as thirty branches or secondary funicles, each terminating in an 

 ovule. The campylotropous ovules are thus brought into the very centre 

 of the ovary, and the conducting tissue of the ovary consists of a number of 

 papillfe or hairs containing starch-grains, which clothe the concave side of 

 the primary and secondary funicles. In C. tortuosus not more than one- 

 twentieth of the ovules are impregnated. M. Guignard was unable to 

 detect any perforations or punctatious at the apex of the pollen-tube, and 

 believes that the passage of its contents into the oosphere takes place by 

 diffusion. He regards the synergidas as playing an essential part in the 

 impregnation of the oospheres, though their exact function is still uncertain. 

 In C. tortuosus it may be as much as three weeks after pollination before 

 the jjollen-tubes reach the ovules. 



Fertilization of Cassia marilandica.^— Mr. T. Meehan describes the 

 mode in which the flowers of this plant are fertilized by humble-bees, the 

 only mode in which fertilization can take place. The anthers do not split 

 longitudinally, but have a terminal pore, covered by a membrane ; the bees 

 burst this membrane, and force out the pollen through the open pore. 

 Mr. Meehan maintains that the dependence of a plant on insect aid for 

 fertilization is an indication that its race is nearly run, and that it is on the 

 downward track in the order of nature. 



(2) Germination. 



Loss of Nitrogen by Plants during- Germination and Growtli.§— 

 Mr. W. O. Atwater and Mr. E. W. Eockwood give the details of some 

 experiments, which consisted in causing peas to germinate under appropriate 

 conditions, and cultivating the germinated plants for a longer or shorter 

 time in water or sand. The nitrogen in the seed at the outset was estimated 

 by determining the nitrogen in other peas in the same lot ; in the germinated 

 seeds or young plants it was determined directly. The general conclusions 

 arrived at may be summarized as follows : — 



(1) The decomposition of nitrogenous organic matter, living and dead, 

 and of nitrates as well, is often attended by the evolution of nitrogen in 

 either the free state or in its compounds, or in both. This liberation of 

 nitrogen is sometimes, if not always, due to microbes. 



(2) The germination of seeds is sometimes, but not always, accompanied 

 by loss of considerable quantities of nitrogen. The balance of evidence 

 seems decidedly to favour the hypothesis that germination without microbes 

 and without the liberation of nitrogen is the normal process. 



* Bull. Soc. Bot. France, viii. (1886) pp. 276-80. 



t See this Journal, 1885, p. 270. 



I Proc. Acad. Nat. Sci. Philadelpliia, 1886, pp. 314-S. 



^ Amer. Chcm. Jouru., viii. (1886) pp. 327-43. 



