ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 591 



bit-is, and the author favours the view that it was a separate unisexual 

 flower, independent of the female strobilus, both flowers having been 

 reduced from a primitive bisexual flower. 



Physiology of Pollen.* — Y. Tokugawa publishes a paper dealing 

 with the physiology of pollen in special relation to the sterility of plants 

 towards pollen of another species. Experiments have been made upon 

 numerous species of Dicotyledons and Monocotyledons with the follow- 

 ing results. For germination a certain amount of moisture is necessary, 

 and in some species a special stimulating agent must also be present. 

 For growth of the pollen-tube suitable osmotic pressure and food- 

 materials are indispensable, although a certain amount of growth may 

 take place in the absence of external food-material at the expense of the 

 reserve material of the pollen itself. Different species of pollen vary in 

 their susceptibility to injury by organic salts, but generally salts of the 

 heavy metals are more injurious than those of the light ones. The 

 duration of life of the pollen-grain is considerably influenced by varia- 

 tion in the amount of moisture present. Albumin and the various 

 forms of sugar are important as means of stimulating the growth of 

 pollen-tubes, each species showing a specific attraction to one or other 

 of these substances. A similar but more marked specific affinity is seen 

 in the food reserves of the pollen-tubes, which consist of either albumin 

 or sugar. The pollen-tubes are drawn into the stylar canal and the 

 micropyle by chemotropic action, but growth along the stylar canal is a 

 mechanical process. The pollen of any species of either a Dicotyledon 

 or a Monocotyledon can germinate, and even attain a certain stage of 

 growth, on the stigma of another species, but even when there is no 

 mechanical hindrance it cannot reach the ovary ; this is possibly due to 

 lack of some specific food-material. 



Nature of Peloria.f — M. J. Sirks publishes a paper dealing with 

 the nature and cause of peloric flowers. The first two sections of the 

 paper are devoted to a historical and critical summary of previous 

 work done in connexion with this subject, while the three remaining 

 sections give an account of the author's investigations as to : — 1. The 

 essential differences between the floral development of normal and of 

 peloric races of Antirrhinum. 2. The connexion between the anatomy 

 of peloric and of normal floral shoots. ?». The indication of gamo- 

 gemrny in peloric flowers of Linaria. It is shown that the develop- 

 ment of the zygomorphic flowers of Antirrhinum differs from that 

 of normally peloric flowers : the latter may be so modified by such 

 secondary phenomena as fascination, as to be apparently the result of 

 gamogemmy ; but the venation of both the zygomorphic and peloric 

 flowers follows the same scheme, so that there can be no question of 

 gamogemmy. Anatomical investigation proves that the course of the 

 bundles of peloric flowers may vary when fasciation occurs. The in- 

 vestigations dealing with Linaria were not sufficiently conclusive, hut 

 pointed to the same results. The author concludes that peloria is a 



* Journ. Coll. Sci. Tokyo, xxxv. No. 8 (1914) pp. 1-53 (2 figs.). 



+ Arch. Neerlancl. Sci. Exact, and Nat., Ser. 3, B. ii. (1915) pp. 239-83 (3 figs.). 



