618 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tion-band in a spectrum. In solutions of chlorophyll in ether and of 

 purpurin in alum he obtains different results from Eeinke. 



To this Eeinke replies * that in the case of purpurin Stenger's results 

 are vitiated by the use of a solution in alum instead of one in alcohol ; and 

 with regard to alcohol, repeating the experiments with a solution of the 

 chlorophyll of Elodea canadensis in alcohol, and one of Aspidistra elatior in 

 ether, he confirms his previous results that the chlorophyll-band III does 

 not correspond in either case to a maximum of the absorption-curve. 



(3) Movement. 



Movements of Tendrils.f — Prof. D. P. Penhallow has investigated the 

 mechanism of movement in Cucurhita, Vitis, and Mdbinia. He agrees with 

 Gardiner and others in connecting the phenomenon of continuity of proto- 

 plasm with that of a distinct transmission of impulses to parts at a greater 

 or less distance from the centre of irritation. This continuity appears most 

 prominently in the coUenchymatous tissue of the rather thick hypoderm ; 

 it may also be observed in the meristem of all parts external to the xylem- 

 portions of the vascular bundles. 



The results are, to a large extent, confi.rmatory of those already pub- 

 lished. With regard to the average rate of movement ; from a total of 436 

 distinct observations on Cucurhita maxima and Pepo under all conditions of 

 temperature and humidity, the average rate of movement was found to be 

 0" 316 cm. per minute. The maximum rate varies very widely ; occurring 

 in waves in the same tendril. 



In the case of Vitis cordifolia, the main facts were found to be in general 

 accordance with those of Cucurhita. Movements of circumnutation were 

 found to arise through unequal growth of the tissues, represented chiefly 

 by the vibrogen bands. The bands of more active growth are strictly 

 localized. Movements due to irritation depend upon continued elongation 

 of the opposite side, together with cessation of growth and contraction in 

 the irritated parts. 



In Bohinia pseudacacia the leaves are characterized by a nyctitropic or 

 true sleep movement. The soft tissue of the pulvinus is that in which the 

 variations of tension under external influences is determined. The pulvinus 

 of the whole leaf appears to determine the upward movement, while the 

 included fibrous elements determine the downward and reflex movements. 

 The various stages in the movements of the leaves and leaflets are described 

 in detail. 



Additional observations are also given on plants belonging to 22 species 

 of 9 genera of Cucurbitacese, and the points described in which the tendrils 

 differ from those of Cucurhita. 



Eotation of Tendrils.J — Herr J. Wortmann states that rotating move- 

 ments sometimes take place in tendrils, in which the angles produced by 

 the rotation change, thus resembling in all respects the movements of 

 twining stems. As a rule the movements of tendrils are very much more 

 irregular than those of twining stems ; nor is the constancy of the same 

 species always maintained as respects rotating to the right or to the left ; 

 occasionally the same tendril will coil in two opposite directions in different 

 parts. With regard to geotropism, Herr Wortmann states that tendrils 

 exhibit this property in the negative sense. Experiments which serve to 

 demonstrate this are described in detail. 



* Bot. Ztg., xlv. (1887) pp. 271-5. 



t Trans. Roy. Soc. Canada, iv. (188G) pp. 49-83 (.3 pis.), and Canadian Record 

 of Sci., ii. (1886) pp. 241-50. Cf. this Journal, 1886, p. 652. 



$ Bot. Ztg., xlv. (1887) pp. 49-55, 65-72, 81-6, 97-100, 113- 20, 138-41 (4 figs.). 



