842 SUMMARY OF CURRENT RESEARCHES RELATING TO 



vulgaris. "Hyph8B"for a similar purpose occur in the stem and 

 mid-rib of tlie leaf in Fucacese. Strongly thickened mechanical cells 

 are found in the centre of the organ in Odonthalia dentata, or forming 

 a ring round the conducting tissue in Cystoclonium purpurascens. 

 The vegetative branches are matted together into a felt-like structure 

 in Ectocarpus tomenfosus. Finally certain branches develope into a 

 kind of tendril embracing other algae, as in Cystoclonium purpurascens 

 var. cin-Jiosa. 



The same purpose is served in other ways by the whole thallus 

 being expanded flat or united into a cushion, mucilaginous in 

 Calothrix scopulorum, incrustaceous in Melobesia, or enveloped in a 

 mucilaginous envelope in Nemaleon multifidum. The stem creeps 

 and is fixed by haptera in PolysipJionia rhizoides ; or the alga grows 

 up among other more resistant species, by which it is protected, as 

 for example Ascophyllum hulbosum. 



The assimilating cells are distributed over the surface of the 

 organ ; but are sometimes, as in Ghordaria flagelliformis, arranged in 

 radial rows. 



The conducting system consists largely of long and narrow 

 hyphse, the transverse walls of which are swollen quite after the 

 manner of sieve-tubes and perforated by extremely fine orifices ; and 

 these conducting hyphae are in communication throughout the plant. 



New Epiphytic Floridea.* — Herr M. Mobius describes a 

 minute epiphytic alga found on preserved specimens of Centroceras 

 clavulatum (Ag. MS.) from Western Australia. It occurs on speci- 

 mens from this locality only, and only on the tetrasporangia, in the 

 form of a large central cell enclosed in a small-celled tissue. In the 

 latter are found not only male and female organs, but also tetraspores, 

 all on different individuals, but closely packed together on the same 

 host. For this epiphyte the author proposes the name Episporium 

 Centroceratis. The tetraspores are formed from simple swollen ter- 

 minal cells, and are dispersed in large numbers among the superficial 

 vegetative cells. They arise by tetrahedral division, and form a body 

 of about 0'016 mm. diameter. The female specimens put out nume- 

 rous trichogynes, but the development of the carpogenous cells and 

 cystocarps is diflS.cult to follow. The trichogyne is often of con- 

 siderable length, and is seated on a trichophore composed of two or 

 three smaller cells, which appear to arise from some larger carpo- 

 genous cells. The male individuals are densely covered on their 

 surface by minute cells, about • 003 mm. in diameter, the antheridia, 

 which spring singly or in pairs at the apex of a terminal cell of the 

 thallus. While the form of the male and female organs of Episporium 

 resembles in its general features that of other Florideae, the structure 

 of the thallus differs so widely from any hitherto known that it must 

 be regarded as the type of a new section. 



Conjugation of Rhabdonema arcuatum.t — Mr. T. H. Buffham 

 describes the phenomena noticed in the process of conjugation of 



* Ber. Deutsch. Bot. Gesell., iii. (1885) pp. 77-80 (1 pi.). 

 t Journ. Quekett Micr. Club, ii. (1885) pp. 131-7 (2 pis.). 



