ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 453 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Structure and Development. 

 Vegetative. 



Winged Stele in some Leguminosse.* — Ph. van Tieghem has in- 

 vestigated the stele of certain Leguminosas, and finds among the sub- 

 tribe Spartiese the normal type and three modifications, viz. (1) stele 

 winged by the pericycle ; (2) stele without wings, but accompanied by 

 meristeles derived exclusively from the pericycle ; (3) winged stele 

 accompanied by meristeles derived exclusively from the cortex. Each of 

 these modifications is found in several genera, e.g. the first in Erinacea 

 and the Furze, the second in Sarothamnus and Spartium, which are thus 

 shown to be nearly related to one another. On the contrary, certain 

 genera share their species among these modifications and the normal 

 type ; the species of these genera are therefore more remote from one 

 another than would be expected for members of the same genus. 



The author suggests that where the flower and fruit show little 

 agreement, e.g. in the Brooms and Trefoils, there should be a thorough 

 investigation of the vegetative structure, especially of the stem ; species 

 with different structure should be placed in different genera ; and 

 also, perhaps, where flower and fruit permit, those with the same structure 

 should be united in the same genus. 



Reproductive. i, 



Pollen-Grain of Picea excelsa.j — J. B. Pollock finds that in the 

 pollen-grain of Picea excelsa the prothallial cells vary in number from 

 one to three ; the former obtains in the majority of cases, while the latter 

 is rare. The position varies, but is usually in a continuous row with 

 the stalk cell and central cell. Since the membranes of prothallial cells 

 sometimes persist after the disappearance of the protoplasm, they are 

 then probably of cellulose. In double pollen-grains, the 3-4 cells 

 lying along the dorsal side are not to be regarded as a prothallium 

 of unusual size, but as the smaller portion of a pollen-grain divided 

 into two unecpial portions, each of which is a potential antheridium. 

 The cells of the larger portion are similar to those in a typical pollen- 

 grain ; the smaller portion varies more, but has a distinct resemblance 

 to the typical antheridium. 



The author concludes that variation in the pollen of Gymnosperms 

 and of Angiosperms indicates reduction by gradual modification, due to 

 disuse of vanishing structures. Suppression of the male gametophyte in 



* Joum. de Bot., xix. (1905) pp. 185-97. 

 t Amer. Nat., xl. (1906) pp. 253-81 (1 pi.). 



