154 NOTICES OF BOOKS AND MEMOIRS. 



ViLLARsiA cAMBODiANA, Hauce {GreutiauaceaB. ) — Cambodia. 

 (Journ. Bot., p. 335.) 



Xylopia Pierrei, Hance (Auonacese.) — Cambodia. (Jourii. 

 Bot., p. 328.) 



Zanthoxylon paniculatum, Balf. f. (Kutacese.) — Rodriguez. 

 (Jourii. Liiiu. Soc, xvi., p. 12.) 



Zygopetalum Clayii, Bchh. f. (hybrid Z. maxillare x crinitum.) 

 (Gard. Cliron., i., p. 684.) 



Troisieme Memoire siir les Mucorinees. Par M. Ph. Van Tieghem. 

 (Ann. des Sc. Nat., Ser. vi., tome iv., p. 312). 



This tliii'd memoir is prefixed by some general observations on 

 classification from the author's now well-known x^oint of view, and 

 by a study of some general questions bearing on the special group 

 the knowledge of which he has done so much to advance. This 

 study is at first concerned with the mutilation and fragmentation 

 of reproductive cells. To deal with this, zygosj^ores of Spoyodinia 

 (irandis and of Sjnnellus fusi(/er were chosen on the one hand, and 

 asexual spores of Piloholiis (Edipm, Phycomijces nitens, and Mortierella 

 reticulata on the other. A preliminary necessary condition was 

 found to be that the body to be mutilated must be proximately 

 homogeneous ; so that with zygospores the experimentation must 

 occur either before perfect maturity, or after commencement of 

 germination when the oil has disappeared : a second condition is 

 that the fragment be not too small. 



The X)rocess was thus conducted : — Buddings from a zygospore, 

 germinating in a humid atmosphere, were cut off as they appeared ; 

 after a time the contents of the zygos^jore divided into a number 

 of spores, separated by interstitial matter : the same result was 

 obtained by similar treatment of an asexual spore ; and if Schizo- 

 mycetous organisms were admitted into the culture-fluid, these 

 endospores were produced without scission of buds. 



The author then passes on to consider the cause which favours 

 formation of zygospores, which he continues to find m the air 

 being impoverished of oxygen. After this he details the dift'erences 

 in the germination, in different media, of spores and zygospores ; 

 and then he treats at length of the structure and mode of de- 

 hiscence of the sporange in Pilobolus and Pllaira. Then follows 

 the systematic portion, in which are described three new species of 

 Piloholus; a new genus (Absidia) with four species; two new specific 

 forms referred to Phizopus ; a new Helicostijlum, with relegation of 

 Circinella (jlomerata, of the first memoir, to this genus ; a Thamni- 

 dium; three new sj)ecies of Mortierella, and the same number 

 belonging to SyncepJialis. 



The new genus Ahsidia has, roughly si)eaking, the asexual 

 growth of Pihizopus and the sexual growth of Plnjcomijces. From 

 the former it differs chiefly in that the sporangiferous stolons have 

 a parabolic form and are cuticularised throughout ; that the spo- 

 rangia alteriiate with the rootlets instead of being superposed to 



