:',7i SUMMARY OF CURRENT RESEARCHES RELATING TO 



stems of Robinia Pseudo-Acacia, Rhus glabra, Populus tremuloides, and 

 Ricinus communis show no increase in mechanical Btrength, or in the 

 amount or kind of mechanical tissue under the influence of longitudinal 

 compression. In the young herbaceous Btems of Helianthus annuus, 

 Vicia Faba, and Phaseolus vulgaris, the development of mechanical 

 ngth in the tissues is somewhat retarded by a longitudinal compn 3- 

 sion caused by comparatively heavy weights. Neither light nor heavy 

 weights have any appreciable effect upon the growth and strength of 

 herbaceous stems which have already formed a cylinder of mechanical 

 or woody i issue. Continuous longitudinal compression causes no marked 

 differences in size or form of any part of the stem which is subjected to 

 the compression, excepting, of course, mechanical changes which might 

 lie cause! by excessive compression. 



Mechanism of Movement in Graminese.* — Z. Woycicki has investi- 

 gated the movement-mechanism of the flowering branches of the 

 Gramineas. After reference to the swollen bases of the leaf-sheaths and 

 the swelling of the lodicules, the author gives special attention to the 

 masses of tissue found on one or both sides of the angle, made by the 

 flowering branch and axis, through which movement takes place, and 

 shows that these last structures must be regarded as differentiated por- 

 tions of the stem for a special function. The epidermis of these cushions 

 is sometimes thickly covered with hairs, and the epidermal cells differ 

 in form and arrangement from those of the ordinary epidermis. The 

 outer part of the cushions is composed either of thick or thin-walled 

 parenchyma, with more or less numerous intercellular spaces, while the 

 interior is of a collenchymatous character. Most frequently the sclereii- 

 chymatous ring of the stem is replaced in the neighbourhood of the 

 cushion by a patch (often horse-shoe shaped) of sclerenchymatous and 

 conducting tissue, upon which the movement-mechanism rests. In other 

 cases the supporting structure is a wedge-shaped mass of sclerenchyma 

 and collenchyma. The power of movement depends almost exclusively 

 upon the turgidity of the cells of the cushion, which is due to the 

 presence of nitrates or nitrites, although the swelling of the cell-walls 

 frequently plays an important part. At the time of movement the cells 

 of the cushions increase in size in the radio-horizontal direction. This 

 movement can take place even after growth of the tissues has ceased 

 owing to the turgor of the intracellular spaces, provided that the cell- 

 walls have not lost their elasticity. 



General. 



Pollination Experiments with Anonas in South Florida.f— 

 I'. <i. Wester draws attention to A. squamosa L. (sugar apple), 

 A. reticulata L. (custard apple), and A. Cherimolia Mill, (cherimoya), 

 and A. glabra, the last named being indigenous. The two first named 

 species have fruited fairly well, hut never abundantly. The failure of 



* Bot. Centralbl., xxvi. 2 (1910) pp. 188-340 (151 figs.). 



t Bull. Torrey Bot. Club, xsacvii. (1910) pp. 529-39 (figs, in text) 



