ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 617 



E. Wulff * continues the work of Figdor by experiments with a view 

 to testing the power of D. clavseformis to transform (under the influence 

 of external factors) the growing-point of the root into that of the shoot, 

 and vice versa. He was successful in changing a root growing-point 

 into a shoot growing-point, but the opposite was a failure. The author 

 regards light as the determining factor in this transformation ; how far 

 gravity and conditions of correlation take part in it is not determined. 



Vaucheria.f — P. Desroche has proved by experiment that Vaucheria 

 terrestris and V. geminata are, in reality, two forms of adaptation of one 

 and the same species, capable of living aerially or aquatically. The one 

 or the other of these forms is produced according to whether the plant 

 grows in contact with the air or in a nutritive solution. The author's 

 experiments were made on carefully isolated cultures of V. terrestris, 

 which in a sterilized Knop solution of 2 : 1000 developed all the 

 characters of V. geminata. 



The same author J in a later note describes a further transformation 

 in the same culture. In one of his five tubes he noticed that sixteen 

 out of his thirty-one examples showed the characteristic form of 

 V. geminata ; the others were all abnormal, the abnormalities being all 

 of the same type. Each of the two symmetrical oogonia is replaced by 

 a hermaphrodite group formed by an antheridium and two oogonia, and 

 each of these oogonia may be replaced in its turn by a similar group. 

 Thus there are formed cymes in which all the branches are terminated 

 by antheridia, except the branches of the last generation, which bears 

 oogonia. The most developed cyme observed showed branches of the 

 third generation, and it seems as if the power of growth was unlimited. 

 It appears also that the sex of a bud is not absolutely determined, and 

 that even when a bud has begun a differentiation into an oogone, its 

 differentiation may be arrested and replaced by vegetative growth ; that 

 then the female determinism of the bud disappears to give place to a 

 sort of sexual indifference, represented by hermaphroditism, 



Caulerpa prolifera.§ — J. M. Janse continues his studies on this 

 alga, and in the present paper gives the result of his experiments in 

 deciding the influence which is exercised by basipetal impulsion on 

 regenerating organs. In a former paper he dealt with the power of 

 organs in Caulerpa prolifera to replace injuries with organs of a similar 

 character, and the present work amplifies his previous conclusions. The 

 first part treats of regeneration, with details as to the experiments, and 

 the second with the actual change of organ caused by injury to young 

 portions of the alga. Experiments on a young leaf -embryo showed that 

 it might be entirely checked, or it might continue its growth as a leaf, 

 or it might form either rhizoids or a rhizome. These possibilities are 

 discussed at length, and then the two questions are propounded. 1. 

 How comes it that the leaf-embryo so often changes its natural design 



* Ber. Deutsch. Bot. Gesell., xxviii. (1910) pp. 264-68. 



t C.R. Soc. Biol. Paris, lxviii. (1910) pp. 968-9. 



X Tom. cit., pp. 998-1000. 



§ Jahrb. wiss. Bot., xlviii. (1910) pp. 73-111 (2 pis.). 



Oct. 19th, 1910 2 T 



