o 



10 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Anatomy and Movements of Porliera hygrometrica.* — A. Rodrigue 

 gives the results of his study of this member of the order Zygophyllaceae. 

 The young leaves and those on the principal stem show incomplete 

 movements ; the other leaves show an oblique movement of the rachis 

 followed by an oblique but slower movement of the leaflets. The move- 

 ments vary from day to day with the intensity of direct sunlight ; the 

 movements cannot be induced. Porliera sleeps from 6 p.m. to 8 a.m. 

 and often also in the middle of the day. The existence of a palisade 

 layer on both faces of the leaf allows assimilation to take place during 

 the midday sleep. 



A considerable development of collenchyma was found in all the 

 motile parts. The movement curves are explained (a) by furrows and 

 ridges in the cortex of the leaf -base ; these are especially developed on 

 one side ; (V) by the very ellipsoidal form of the bundles, especially at the 

 articulation of the leaflets where the cortex is divided into two parts 

 which have no direct communication. The course of the bundles is 

 almost identical in the leaves of the motile Leguminosas, Oxalidea?, and 

 Porliera. No motor swellings occur, there is no local concentration of 

 the bundles or exaggeration of the cortex. Chemical tests do not show 

 the presence of tannin ; its absence suggests that it may perhaps not 

 play the important part which has been assigned to it in the Leguminostc. 

 Nor were plasmic threads found between the cells ; their absence is not 

 surprising as transmission of stimuli does not occur. 



Reproductive. 



Embryogeny of Zamia.f — J. M. Coulter and C. J. Chamberlain de- 

 scribe the results of their study on the embryogeny of Zamia floridana. 

 They note that the ovulate cones continue their development for some 

 time after removal from the plant. The nucleus of the ventral canal- 

 cell is formed, but no definite cell is cut off ; the protuberance in which 

 the nucleus lies rapidly disorganises. Their preparations of the fertilisa- 

 tion stages confirm Webber's account. A period of free nuclear division 

 follows fertilisation ; the mitotic figures of the eighth division, which 

 gives rise to the 256-nucleate stage, were counted. The nuclei are 

 scattered through the egg ; there is no tendency to form the large 

 central vacuole and consequent parietal placing of the nuclei as in 

 Gycas ; the nuclei are more numerous in the lower part of the pro- 

 embryo, but the upper portion is never free from nuclei in the later 

 stages, and it would seem probable that many of the nuclei in the 

 upper part of the proembryo which is not to form any part of the 

 embryo proper, are due to irregular division. Thus Zamia differs from 

 Cyras in the absence of the central vacuole and the parietal arrange- 

 ment of the nuclei. It also differs in the formation of cell-walls, 

 which are restricted to rather a limited area at the base of the egg. 

 The elongating cells of the suspensor can be distinguished at quite an 

 early stage from those of the embryo proper. The rapid elongation of 

 the suspensor forces the embryo down into the endosperm. Owing to 

 the great resistance the base of the embryo is forced upward into the 



* Biblioth. Univers. Arnh. Sci. Phys. et Nut. (Geneva), se'r. 4, xiv. (1902) 

 pp. 513-5. t Bot. Gaz., xxxv. (1903) pp. 184-93 (4 pis.). 



