INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC, 607 



Resting- Condition pf Vaucheria geminata.* — It has long been 

 known tliat the unicellular vegetative thallus of various species of 

 Vaucheria is liable to segmentation as the result of injury, the attacks 

 of parasites, &c. In addition to this, in certain circumstances they 

 are capable of undergoing a change, visible to the naked eye by the 

 brighter green colour by which it is accompanied, in which the fila- 

 ments become divided into a large number of cells of nearly equal 

 size by thick gelatinous septa. In this state they form the genus 

 Gongrosira of systematic works. 



E. Stahl has made a special study of this condition of Vaucheria 

 geminata. The Gongrosira is multiplied by the production of fila- 

 ments from the various cells. A not unfrequent phenomenon is also 

 the escape of the entire contents of one of the cells siu'rounded with 

 cellulose, which thereupon proceeds to germinate. But more common 

 is the breaking up of the protoplasm of a cell into a variable number 

 of portions, at first, as they escape from the mother-cell, enclosed in 

 a thin membrane, which subsequently swells up and bursts. The 

 separate portions of the protoplasm then move about with an amoeboid 

 motion, slowly creeping over the substratum. The motion ulti- 

 mately ceases, the protoplasm assumes a spherical form, and clothes 

 itself with a thin membrane. All these changes may take place, and 

 the resting-cyst be formed, even within the mother-cell. These cysts 

 sometimes develop immediately into new filaments, but more often 

 they remain for a time in a resting condition, in which they entirely 

 lose their green colour. Their germination is marked by the re- 

 appearance of chlorophyll. 



This condition of Vaucheria bears a striking resemblance to one 

 of the forms of another of the Siphonese, Botrydium, described by 

 Rostafinski and Boronin. 



Italian Algae.— The first volume (1878) of the ' Atti della Societa 

 Crittogamologica Italiana ' is chiefly occupied by Ardissone's study of 

 the Italian Algae belonging to the family Rhodomelacese, which 

 comprises the genera Chondriopsis, Acanthophora, Alsidium, Digenea, 

 Pohjsiphonia, Hytipjhloea, Vidalia, Dasi/a,aTid Hanovia. Oi Poh/siphonia 

 alone there are forty-eight species. The volume includes besides a 

 description of a new form of Melosira Borrerii, by F. Castracane ; an 

 enumeration of the diatoms collected at Ostia, by M. Lanzi (a 

 little over 100 species, no novelties) ; and a diagnosis of the genera 

 belonging to the family Hypocreacefe of Pyrenomycetes, by P. A. 

 Saccardo, several of them new. 



Subalpine Desmidiese. — The last part of the 'Mem. della real. 

 Accad. delle Scienze di Torino,' vol. xxs. 2nd ser., is occupied by the 

 continuation of J. B. Delponte's ' Specimen Desmidiacearum siib- 

 alpinarum,' the first part of which was published in 1876. It is 

 intended to be supplemented by additions to our knowledge of the 

 subject which have come to hand since the publication of the first 

 part. The present part is illustrated with fifteen plates, and the 

 whole will form a magnificent monograph of the subalpine Desmi- 

 * ' Bot. Zeit.,' xxxvii. (1879) p. 129. 



2 S 2 



