90 SUMMARY OF CURRENT RESEARCHES ^RELATING TO 



branching or cortication. Griffithsia Bornetiana produces a large 

 spreading holdfast composed entirely of pseudo-parenchymatous tissue 

 arising from the primary root-cell. Callithamnion, Spyridia, and Cera- 

 mium have primary root-cells, from which spring rhizoids terminating 

 in multicellular discs. Others originate in the csll adjacent to the 

 basal cell and in the cortications. 



Melanospermeae.* — Mr. E. A. Bastow gives, in a large sheet, a key 

 to the tribes and genera of the Melanospermeaa (Fucacese and Phaec- 

 sporeae), with a somewhat rough drawing representing the salient cha- 

 racters of the more important genera. 



Plurilocular Sporanges of Petrospongium.t — Mr. H. Hanna has 

 found the plurilocular sporanges of Petrospongium Berkleyi, belonging 

 to the Phfeophycese. He finds a great difference in size between the 

 different loculi in the same sporange, and a consequent inequality in 

 size among the zoospores produced in them. 



Alternation of Generations in the Cutleriaceae4 — After a review 

 of the literature, and a description of the species of Cutleriaceae found 

 in the Gulf of Gascony, M. C. Sauvageau discusses at length the bio- 

 logical connection between the three genera Cutleria, Zanardinia, and 

 Aglaozonia, and the phenomena of polymorphism and parthenogenesis 

 which they exhibit. 



The Cutleriaceae have a sexual and a non-sexual thallus. The sexual 

 plant of Zanardinia is monoecious, and differs from the non-sexual plaut 

 only in the nature of the reproductive organs ; the sexual plant of 

 Cutleria is dioecious. The oogonial and antheridial thalli of Cutleria, 

 like the thallus of Zanardinia, are formed by the union of two layers 

 of filaments, which subsequently increase in surface and thickness 

 from the further division of the cells. On the other hand, the zoospore- 

 thallus (^Aglaozonia'), is a creeping plate composed of a parenchyme, and 

 resembling a Zonaria in external appearance. 



M. Sauvageau considers the " alternation of generations " between 

 Cutleria and Aglaozonia to be a facultative rather than a necessary one. 

 "While there is certainly a biological connection between C. multifida 

 and A. parvula, that is not the case with C. adspersi and A. chilosa. 

 The non-sexual form of C. adspersx appears to be A. melanoides ; the 

 sexual form of A. chilosa being at present unknown. The germination 

 of fertilised or of parthenogenetic oospheres of a Cutleria may give rise 

 to an Aglaozonia ; while under other conditions they may produce 

 agaiu a Cutleria ; and the same is the case with the zoospores of 

 Aglaozonia. From whichever reproductive element an Aglaozonia 

 originates, it is not a direct product of germination, but a secondary 

 product, always formed by a pro-embryo or colonerette. 



Growth of the Chlorophyll-bands in Spirogyra.§— Herr. R. Kolk- 

 witz infers, from the phenomena presented in the case of S. longata, 

 especially the behaviour of the pyrenoids during the growth of the 



* Journ. and Proc. R. S. New South Wales (1899) pp. 169-73 (1 pi.). 



t Ann. of Bot., xiii. (1899) pp. 4(51-4 (1 fig.). 



X Ann. Sci. Nat. (Bot.), x. (1S99) pp. 265-362 (1 pi. and 25 figs.\ Comptes 

 Rendus, exxix. (1899) pp 555-8. Cf. this Journal, 1898, p. 565. 



§ Fetschr. f. £chwendener, 1899, pp. 271-87 (5 figs.). See Hedw ; gia, xxxviii. 

 (1899), Beibl., p. 204. 



