ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 831 



layer, in immediate contact witla the endospore, is always thin, per- 

 fectly homogeneous, and cuticularized ; with iodine and sulphuric 

 acid it takes a yellowish or brownish colour. The middle layer is 

 suberized ; it is rarely hornogeneous, but usually finely granular, and 

 is composed of very thin round or angular columns, placed very 

 closely at right angles to the surface ; it is sometimes altogether 

 wanting. The third and oxitermost layer is composed of cellulose, 

 and varies greatly in its development. Its outermost portion is dark 

 brown, and cuticularized or suberized. 



In Peronospora, on the contrary, the exospore consists (with only 

 one exception among the species examined) of only two layers ; an 

 inner one, corresponding to the innermost in Cystopus, and an outer 

 granular layer which makes up by far the larger part of it. Both 

 the layers are cuticularized, and contain no cellulose. 



The mature oospore of Cystopus contains a ball of protoplasm, 

 occupying from one-half to nearly two-thirds of its diameter, which 

 itself contains a large amount of oil ; the protoplasm between this 

 ball of protoplasm and the wall of the oospore is dense, and nearly 

 homogeneously granular. In its outer portion are a number of 

 bright round spots, which may be vacuoles, or possibly may consist 

 of hyaloplasm. 



The author describes the following species : — C. candidus Pers., 

 parasitic on CruciferaB and a few Capparideae ; G. sibzricus Zlski., on 

 an undetermined plant belonging to the BorragineBB ; G. convolvula- 

 cearum Otth., on Gonvolvulus and Batatas ; G. Portulacce DC, on 

 Portulaca ; G. Amarantacearum Zlski., on Amarantacece (not on Ama- 

 rantus Blitum) ; G. Bliti Bivon, on Amarantus Blitum ; G. cubicus 

 Strauss, on Compositse ; G. Lepigoni dBy., on Lepigonum. 



Zygospores of Mucorini.* — G. Bainier has studied the conditions 

 which favour the production of zygospores in the Mucorini, and finds 

 that the conditions vary in the different species. The absence of free 

 oxygen or of light is not a necessary condition, nor is a deficient 

 supply of nourishment always requisite for the production of zygo- 

 spores. Bainier cites a considerable number of cases where he has 

 cultivated different species, and gives the manipulations required in 

 each case for securing sporangia and zygospores ; and he adds some 

 observations on the chemical action of certain species. Thus, Piloholus 

 roridus cannot be cultivated on fluids, but only on semi-solid sub- 

 stances ; Bhizopus, on the contrary, grows on all saccharine or starchy 

 fluids, on mouldy bread, but developes only imperfectly on horse- 

 dung. Thamnidium and Ghcetostylum develope better on a solution of 

 peptone or of extract of malt than in a decoction of plums ; the species 

 of Mortierella flourish greatly when cultivated on raw meat. 



Phycomyces nitens, which usually grows on fatty substances, which 

 it decomposes, can also be cultivated on cochineal, causing it to assume 

 a deeper colour, and rendering it more valuable commercially. Mucor 

 racemosus, and a new species, M. tenuis, are described and illustrated 

 in full. 



* Anu. Sci. Nat. (Bot.), xv. (1883) pp. 342-56 (3 pis.). 



