25 



Reviews of Foreign Literature. 



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In a Dissertation by Paul Hauptfleisch, Greifswald, 1888, on 

 the Cell-membrane and gelatinous Envelope of the Desmids, the 

 author states that with the exception of Spirotaenia, which does 

 not properly belong to the Desmids, the cell-membrane of the 

 entire family consists of two separate pieces, the thin edges of 

 which overlap each other in a similar manner to the membrane 

 pieces of the Diatoms. Many species of Closterinm diixd Peninm 

 correspond still more closely to the Diatoms by having the so- 

 called shells and girdle bands of the latter. When the cells divide 

 a new cylindrical membrane is first formed under the place of 

 meeting of the two pieces of the old, and when the two halves are 

 shoved apart, the new membrane is thus exposed, after which 

 a cross portion divides it in two cells. The completed membrane 

 is in most cases provided with small pores; extending through 

 these are fine protoplasmic threads, which terminate on the outside 

 in small head-like expansions. The gelatinous covering of the 

 membrane consists of separate portions covering certain parts, and 

 these portions are composed of prismatic bodies fitting closely 

 into each other. 



Although no clear exposition of the functions of these pores, 

 nor of their relation to the rest of the plant, is given by the author, 

 he states emphatically that the exudation of gelatinous substance 

 takes place through them and that they are not formed till the 

 membrane is otherwise perfect. ' E. L. G. 



The so-called Spermatia of the Ascomycetes. By Alfred Moeller, 

 (Bot Zeitung, July 6th, 1888.) 



This is the subject of a brief article in reference to certain 

 criticisms on a previous article, " The Culture of Lichen building 

 Ascomycetes without Algae," in which the author has given 

 strong evidence in favor of the conidial nature of the supposed 

 spermatia of the ascomycetes. In the article in the Bot 

 Zeitung, he sums up the evidence in favor of the theory of the 

 sexual nature of the spermatia, and then the evidence on the 

 other side, and states that there is no longer any reasonable 

 ground for the assumption of the sexual function of these organs. 



