ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 605 



action of hyphse and algal cells ; it is not a true parasitism, since the 

 alg8e are not destroyed or weakened by the fungal hyphte ; nor can it 

 be regarded as a true example of hypertrophy of the algal cells. 

 There is no struggle for existence between algaB and hyphfe. The 

 author was unable to detect the mode in which the algal cells pene- 

 trate into the thallus, but each seems to impart nourishment to the 

 other. 



The author regards cephalodia as always the result of an acci- 

 dental meeting of alga and lichen, the former constituent always 

 belonging to a type of very wide distribution ; but there must also 

 always be some power of adaptation of one to the other ; some forms 

 of lichen, as Cladonia, appear never to form cephalodia. If 

 Schwendener's hyj)o thesis is regarded as one of mutual symbiosis of 

 algae and fungi, rather than as one of parasitism, then the occurrence 

 of cephalodia supports it rather than otherwise. 



Thallus of Lecanora hypnum.* — K. B. J. Forssell describes the 

 somewhat peculiar structure of the thallus of this lichen. It consists 

 of an incrustation of small yellowish-brown rounded granular scales, 

 which do not form a continuous layer, but the whole lichen consists 

 of a complex of individuals more or less cohering in their growth. 

 The scales are of two kinds, one with yellow-green, the other with 

 blue-green gonidia. The author is doubtful whether the latter are 

 to be regarded as cephalodia, or as belonging to a different lichen- 

 species, Pannaria pezizoides. Apothecia occur, on the under side of 

 which are sometimes cephalodia containing cells of a Nostoc. 



Algae. 



Systematic Position of Ulvaceae.t — The third part of J. G. 



Agardh's series of Monographs of Algae is devoted to the Ulvaceae. 

 Differing from Berthold's view,| he places the genera Bangia and 

 Porphyra among the Ulvaceae, and not among the Florideee. In this 

 he relies chiefly on the difference of the reproductive organs in the 

 Ulvaceae and Florideae, the former possessing true zoospores, the 

 Florideae antheridia, cystocarps, and tctraspores. The quaternate 

 division of the cells in the two genera in question he regards as 

 showing an affinity not so much with the tetraspores of Florideae, as 

 with the mode of division in Prasiola, Tetraspora, Palmella, Mono- 

 $troma, and some species of Ulva and Enteromorpha. There is also a 

 very material difference in their physiological value, the octospores 

 of Porphyra being regarded as sexual, the tetraspores of the Floridoje 

 as non-sexual. There is at present a very considerable divergence 

 between the description by different writers of the organs of repro- 

 duction in Bangia and Porpjhyra. 



The Ulvacoao are divided by Agardh into eleven genera :— Gonto- 

 trichum, Erythrotrichia, Bangia, Porphyra, Prasiola, Mastodia, Mono- 



* Flora, Ixvii. (1884) pp. 187-93. 



t Agardh, J. G., 'Til Algemes Kystcmatik :' Lnnda Araekiift, xix. (4 pis.) 

 (Latin). ii>-o Nature, xxix. (1884) p. MO. 

 I beo tliia Journal, ill. (188:5) p. 408. 



