THK OEKMIXATIUX OF SI'OKES. 29 



Kistinj; powers of the ascospores of Sw, ,,n,,,,,<i/reteis, an«l lii.- 

 pnicticiil foiiseqiiunces tlu-it^of, moio will liuvo to bo isuid in a 

 Liter cliuptL'r. In the aisti of ni.iny funj^i, the resting cells muHt 

 reumin (|uie.seent for n ci'itjiin i»i'rio<l liL-fore they beconie c-upahle 

 of gernunatin<^. This apiilifs particularly to the whole of the 

 zygospores and oospores. ( )n prolonged exposure to the air the 

 contents of the spores grailually dry up, so that the luendjrane 

 soon heconies wrinkled ; I)ut iniiiiersion in water causes them to 

 swell nut and rouiue tlicii' phnuimess. 



The power of resisting heat varies according as the heat acts 

 on the fungus spikes in the dry state (vj 7O) or in presence of 

 moisture ; in the latter event they die off much mcHe readily 

 and speedily. Thus, it was shown hy Pa.steur that the conidia 

 of Penin'llium ylaucum perish when dilfused in a litiuid at 100° C, 

 whereas when moisture is excluded they will resist a tempeni- 

 ture of 120" 0. for some tinje, though incapalde of .standing 

 I 27° to 130° C Further particulars under this head will be given 

 in the paragraphs dealing with the moulds growing on bread, 

 itc, in a later .section. 



Divergent opinions have been expressed as to the cause of 

 the high resistance presented to dry heat by the spores of 

 Kuiiiii<-etes. E. CiiAMEK (III. and IV.), on the basis of certiin 

 chemical analyses, ascribes this property to the high concen- 

 tration of the cell contents, the residual water being insuthcient 

 in quantity to allow of the coagulation of the albuminoids. He 

 found, for instance, ab(Ait 61 per cent, of dry residue in the 

 spores, but only about 12 per cent, in the coriesponding mv- 

 celium ; though in the former the ash content (3.1 per cent.) 

 was smaller than in the latter (i 1.3 per cent.). In view of the 

 alreaily emphasised dependence of the chemical compo.Mtion of 

 the micro-organisms (§ 36) on the nature of the nutrient sub- 

 stnitum, it is a somewhat risky matter to draw general conclusions 

 from sudi analytical dat.a. This al.so applies, be it remarked, to 

 the results of tin- chemical analv.ses of the mvcelia of lihizoiius 



• "^ I 



niijricana, Penirillium ifiauami, and Asjunjil/iis 7u'i/cr {(j/aunm f) 

 made by ^lAitscn ai.i. (I.). 



In respect of resistance to low temperatures, what has already 

 been stited in <; ()i applies also, in the main, to the spores of 

 Emuijct'teii. On the other hand, the mycelia, especiallv when 

 rich in .sap, fre(pu'ntly perish at a few degrees below zero C ; 

 e.ij. acct)rding to Mulisch (V.), that of J'lii/ronn/ri'jf nittu,<. 

 Others again, such as pressed yea.st, which is poor in water, will 

 stand very low tempeiiiture.s. 



As regards the resistnince of the spores of J-Juinvretes towards 

 poisons, the ob.servations alreaily recortled in vol. i. mav be 

 supplemented by reference to the works of O. LoEw (II.), B. 

 JoKNssox (I.), and F. L. Stevens (I.). 



We have now learned, in connection with the genenil mor- 



