ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 291 



while the young plants, which in Sargassum are unbranched, without 

 bladders, and densely covered with leaves, would not be wanting if 

 S. bacciferum were a floating pelagic species. 



5. The floating fragments are always in a state of etiolation or 

 decay ; the olive-green colour in reflected light has almost entirely 

 disappeared. 



6. The position of the tufts of branchlets is usually reversed, the 

 apices pointing downwards, and the broken ends of the stems upwards. 



7. There is no regular growth in the floating Sargassum; even 

 the abnormal growth which the fragments often display in the water 

 for a short time, is hypothetical, and has not been accurately 

 observed. 



The plant is variable in almost every single characteristic ; and 

 about 300 different forms have been described as distinct species ; a 

 synopsis is given of the more important. 



The author has come to the conclusion that the ordinary state- 

 ments of a " Sargasso Sea," with a definite and constant area, are 

 not founded on fact. The floating fragments occur throughout the 

 Atlantic Ocean, and the prevailing winds and currents cause them 

 to accumulate sometimes in one part, sometimes in another. 



A fresh classification is appended of all the genera of Fucacea?, the 

 primary division being as follows : — A. Sporanthia (i. e. the pits with 

 the organs of reproduction) dispersed over the thallus. B. Sporanthia 

 upon the bladders. C. Sporanthia on special terminal inflorescences. 

 A new genus, Xi^hophyUanilms, is founded on Blossevillea xiphocarpa 

 Harv. 



With regard to Macrocystis pyrifera, the author doubts the cor- 

 rectness of the statements as to its enormous size, it being stated that 

 the fronds attain a length of 1000 feet. 



Spermothamnion torulosum.* — F. Ardissone has examined perfect 

 specimens of this seaweed, which has been assigned to both Griffithsia 

 and CalUthamnion, and considers it to be a true SpermolJiamnion. The 

 cystocarps must not be confounded with the true favellte of CalUtham- 

 nion, but present the form of a terminal bunch of spores j^'ovided with 

 a common periderm, and surrounded by an involucre composed of 

 branchlets. The spherospores are developed here and there on the 

 branches. They are rounded, and sessile or pedunculate, and with a 

 nucleus divided in three. The antheridia are developed on special 

 branches, are conical in form, and are borne on a large basal cell. 



Genetic Connection of certain Unicellular Phycochromacese.t— 

 In connection with his researches on Glceocystis,t P. Richter suggests 

 whether various forms of unicellular algfe hitherto considered distinct, 

 and ranged under the genera Gloeocapsa, Chroococcus, Aphanocapsa, 

 Gloeothece, and ApJtanothece, are not really genetically connected, dis- 

 playing a kind of polymorphism ; a form with but slightly encysted 

 cells (^Aphanocapsa) intervening between one with encysted spherical 



* Atti Soc. Critt. Ital., xxiv. (1881) p. 24. 



t ' Hedwi;,Ma,' xix. (1880) pp. 169-71 aud 191-G, 



J See this Joui'ual, ante, p. U8. 



