ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 545 



Fixed daylight position of Leaves.* — Ilerr G. Krabbe agrees with 

 A. B. Frank in attributing the fixed position assumed by the lamina of 

 leaves in ditfused daylight to the influence of light without the assist- 

 ance of geotropism or of internal forces. The experiments were made 

 on Dalilia, Fuchsia, Phcisrolus, Pelartjonium, and other plants. The 

 position depends on the hcliotropic projjerties of the leaves themselves, 

 and is unaffected by their weight, even when this is artificially increased. 

 The movements of the leaf-stalk which bring about the diurnal position 

 of the lamina take place only in its upper region ; and these movements, 

 which finally bring the surface of the lamina perpendicular to the 

 incident rays of light, are the result of heliotropism only. This move- 

 ment of the leaf-stalk is of the nature of a curvature, not of a torsion. 

 Torsion of the leaf-stalk is always the result of the co-operation of two 

 distinct forces, such as heliotropism and geotropism, in different planes. 



Structure and Function of the Bladders of Utricularia.f — Herr M. 

 Biisgen has examined the structure of the bladders of TJtricularia 

 vulgaris, for the purpose of determining whether they can have any 

 other function than that of serving for the nutrition of the plant. The 

 suggested purposes of protecting the plant from being devoured, and of 

 serving simply as swimming-organs, he finds to be inadmissible. The 

 number of fresh-water Crustacea, chiefly Cyiiridineae, captured is very 

 large, and the " auteunfe " and long hairs with which the bladders are 

 furnished are admirably contrived to assist these animals in finding their 

 way into the bladders. Around the entrance to the bladder are a number 

 of glandular hairs, from which is exuded a mucilage very difficult to 

 detect in tlie water ; and this mucilage seems to be the attraction to the 

 animals. The cause of death of the animals is not clear ; nor was the 

 actual digestion of their bodies demonstrated ; but a series of experiments 

 carried out by Herr Biisgen on plants in w^hich animals gained access to 

 the bladders and on others where this was imiDossible, showed almost 

 invariabl}' a greater vigour of growth for the former. 



Stomates of Graminese and Cyperaceae.} — Herr S. Schwendener 

 finds that the mechanism of the stomates of the Gramineae and Cyperaceae 

 differs to a certain extent from that of other Angiosperms. The 

 broadened end of the guard-cells ajjpears to j^lay an important part in 

 the process, enlarging the size of the opening by an increase of their 

 turgidity. Only in a few cases could any participation of the adjacent 

 cells in this process be detected. In those si)ecies which inhabit the 

 steppes, the desert, and other arid situations, special contrivances occur 

 to protect the stomates from excessive transpiration ; and these are found 

 also in some species of Carex which inhabit marshes ; these, the author 

 conjectures, must be immigrants from a more northern latitude. 



With regard to the systematic value of the structure of the stomates, 

 he finds that, while their special form in Gramineae and Cyperaceae is 

 peculiar to those orders, and marks them oft' sharply from the Juncaeeas 

 and other allied orders, there are other anatomical characters common 

 to the Cyperaceae and Juncaceae, and others again to the Gramineae, 

 Cyperaccce, and a portion of the Juncaceae. 



* Jalirb. Wiss. Bot. (Pringsheim), xx. (1889) pp. 211-60 (1 fig). 



t Ber. Deutsch. Bot. GeselL, vi. (1888) Geueral-Vers.-Heft, pp. Iv.-lxiii. 



X SB. K. Picuis. Acad. Wiss., 1889, pp. G5-79 (1 pi.). Cf. this Journal, 1882, 



p. 21(3. 



