206 SUMMARY OF CURRENT RESEARCHES RELATING TO 



two genera above mentioned. His first section is devoted to remarks 

 on the sporangia of Halimeda tridens (under which name he refers to 

 what we commonly call H. incrassata) and of H. Tuna. The sporangia 

 of H. tridms have not been hitherto recorded, and they are here com- 

 pared with those of H. Tuna. They are uniformly yellowish-brown or 

 burnt-umber colour, and the sporangiophores are most densely clustered 

 along the upper margins of the segments, especially at the apices of the 

 lobes ; they may, however, emerge from any part of the segment and 

 sometimes completely cover its surface. The author then presents his 

 views on the American species of the H. Tuna group, in which he 

 recognises three distinct species — E. Tuna, H. discoidea, and H. scabra. 

 He attributes a certain amount of importance to the degree of calcifica- 

 tion, as well as to the size and shape of the peripheral and subperipheral 

 utricles. The next section is devoted to a treatment of the American 

 species of the H. tridms group, in which the author describes a new 

 species H. simulans, and recognises three other species. One of these is 

 the H. monile Lam., generally regarded as being a form of PL. incrassata. 

 A key of the four species of this group is given. An important fact 

 is recorded in this paper, namely, the finding for the first time of the 

 sporangia of Avrainvillea, which the author has discovered in the species 

 A. nigricans Decne. They consist of clavate and fusiform to pyriform 

 and subglobose bodies, borne on filaments raised above the surface of the 

 thallus. Sometimes the sporangium only contains a single spore, but 

 the usual number is three, four or five, rarely six, seven or eight. The 

 author regards them as aplanospores. The final section of the paper 

 deals with the American species of AvrainviUea, of which the author 

 describes four with synonymy and key. He adds finally a note on 

 U. tomentosa Murray and U. luteofusca Murray. 



Some Critical Green Algae.* — G. S. "West publishes notes on six 

 members of the Chlorophyceas, about which nothing or little is known. 

 Three of these are new species, and one is transferred to another genus. 

 The first alga dealt with is Polgclmtophora simplex, the discovery of 

 which adds a second species to that genus. The author describes it in 

 detail, and points out the differences between it and Glceochcete Witt- 

 rockiana Lagerh. P. simplex is a member of the Chlorophyceas, and its 

 cells, which are not enveloped in mucilage, are each furnished with two 

 to four simple bristles. G. Wittrockiana, on the other hand, is one of the 

 Myxophyceae, with its cells enveloped in a copious mucilage, and its 

 bristles frequently possess short spuivlike branches. Brachiomonas sub- 

 marina Bohlin is next described, belonging to a genus only observed 

 hitherto from Norway and Sweden. Phyllobiuni sphagnicola is another 

 new species, and constitutes the first recorded instance of a Phyllobium 

 occurring on the leaves of a Sphagnum. Kirchneriella subsolitaria, the 

 third new species, differs from the three previously known members of 

 that genus in the subsolitary habit and the entire absence of mucus. 

 Tetraedron platyisthmum has been known as Cosmarium pi at y isthmian 

 Archer, who recorded it from Ireland. West now finds it in collec- 

 tions of algas from the boggy hollows in the Lewisian gneiss of West 



* Journ. Linn. Soc. (Bot.) xxxviii. (1908) pp. 279-89 (2 pis.). 



