EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 167 



Genus VOLVOX. 



Tail absent ; eye present ; filiform 

 proboscis double; division of cor- 

 puscles compound and unequal. 



Three species have been describ 

 ed : all of a green colour. 



anil ^tracts from dfomgn 



[From Valentin s Repertorium, 1841.] 



Swlibe upon the Development of Boletus destructor.* It first ap- 

 pears, according to him, as a fugitive growth (auflug) of a dirty green 

 colour, consisting of fine, simple, microscopical filaments, somewhat 

 transparent, and covered with minute, round, greenish germ -globules, 

 and in this respect resembles the Dematium virescens (Pers.) This fu- 

 gitive growth is converted afterwards into fine cobweb-like threads, in- 

 terwoven with thicker branched filaments of a yellowish colour. Under 

 the microscope both sorts of filaments appear colourless, exceedingly 

 transparent and curved. One portion of them lies closely together, and 

 they become glued in their position by a yellow resinous substance. 

 The yellow branched filaments become gradually thicker, and at last 

 assume the form of a rhizoma, with a brownish rind and transparent in 

 the centre. The fibres in the latter resemble the colourless one above 

 described. Those of the rind are more slender, less transparent, of 

 a dark brown colour, and interwoven. The outer extremities of the 

 rhizoma-like body, consist of very fine filaments, which have some re- 

 semblance to Oscillatoria punctata. In spring and summer, and especi- 

 ally in a moist atmosphere, they become, as it were, woven into a dry 

 silky texture, on which the germ powder is again formed, whence a new 

 growth of the Fungus commences. p. 81, 82. 



Mohl on the Colouring of Vegetable Membranes by Iodine. From the 

 numerous experiments of Mohl, which are recorded in the Flora, a uni- 

 versal Botanical Journal by Hoppe and Fiirnrohr, and of which an 

 abstract, too long for our limits, is given in Valentin's Repertorium 

 1841, it would appear, that colours varying from brown to blue, may 

 be produced in all vegetable membranes, when placed in a condition to 

 absorb a large quantity of Iodine. A yellowish or brown colour is 

 caused by the application of the Iodine in a state of vapour, and a violet 

 or blue by very concentrated solutions. He further concludes, that the 

 reception of Iodine, and consequently the colouring, is in proportion to 

 the consistence of the membrane. The weaker and softer, and more 

 absorbent membranes, being the more ready to assume the blue colour. 

 Schleiden agrees with these statements, and concludes, as was already 



* Schlechtendahl's Linnrca, p. 194200. 



