702 SUMMARY OF CURRENT RESEARCHES RELATING TO 



These plants become attached when young to the oysters and gradually 

 increase in size. When they have attained a certain size and are left 

 uncovered by the retreat of the tide, they split from the pressure of the 

 water they contain, and this, trickling out, is replaced in part by air. 

 The rising tide imprisons this air, the alga swells, rises, and carries up 

 with it the oyster to which it is attached. The whole thing is then 

 wafted away by currents, and in this way no less than 400,000 oysters 

 have been, according to Fabre-Domergue, removed from the oyster- 

 beds. The same author states that this evil is to some extent mitigated 

 by the drawing of faggots of thorn-bush over the beds, and thus breaking 

 the " balloons." L. Mangin does not consider that this growth of 

 Colpomenia is at all likely to diminish or disappear, but that the favourable 

 conditions created by the Gulf Stream are likely, on the other hand, to 

 encourage a further distribution of it along the Channel shores. 



Germination and Alfinities of Cladostephus.* — C. Sauvageau has 

 succeeded in watching the germination of Cladosteplms verticillatus and 

 has by this means determined for the first time its affinities. As is well 

 known, the plant consists of a creeping thallus which bears upright, 

 " indefinite," deciduous shoots, but the origin of the creeping thallus and 

 the means by which the indefinite shoots arise have been unknown. The 

 author is now able to give information on both points. The zoospore pro- 

 duces first a small compact mass of cells, from which arise several long fila- 

 ments. The first formed are simple, and bear here and there a hair ; these 

 are identical with Sphacelaria. The later filaments are larger and bear 

 several holoblastic branches in the manner of Halopteris with one or two 

 hairs in the axil. Sometimes on vigorous plantlets the same filament has 

 first the character of a Sphacelaria and then of a Halopteris. From the 

 lower surface or from the edge of the small germination-disk, there arise 

 slender rhizoids and long stolons terminated by a " sphacele." The stolons 

 become enlarged here and there by lateral expansions, which produce 

 new upright shoots. Finally, in the middle of the bunch of Sphacelaria- 

 and Halopteris -like shoots, rich in chi'omatophores, rises a larger, less 

 coloured stem, which is one of the indefinite shoots of Cladostephus. 

 The first of its secondary cells are sterile and very early produce 

 corticating rhizoids ; the upper secondary cells bear lateral shoots, but 

 instead of being verticillate as on the adult plant, they are first single or 

 opposite. Only later do the shoots grow verticillately. This likeness of 

 the young plant to the shoots of Sphacelaria and Halopteris is an 

 important guide to the affinities of Cladostephus. 



HaBmatococcus.l — W. Wollenweber has examined species of Hmnato- 

 coccits with a view to deciding whether or no the cells possess an eyespot. 

 On this point there has been some indecision in the past, but this author 

 is able to prove that all the species (3) possess a stigma in all motile 

 stages of development. The presence of a stigma was first proved by 

 him in green forms of H. pluvialis, and he gives details of his methods 

 of preparation, etc. Subsequently, he found the stigma in red forms 



* C.R. Soc. Biol. Paris, Ixii. (1907) pp. 921-2. 



t Ber. Deutsch. Bot. GeselL, xxv. (1907) pp. 316-21 (1 pL). 



