CHEMOTKOPISM. 6i 



conclitiuiLS, tliis tendfiicy is expressed by the excretion of sub- 

 Htances capable of attacking and jn-rforating the siiid paititious. 

 Among such sul)stjinces may be mentioned carbon dioxide and 

 oxalic aciil, which come into action niort' especially when the 

 fungus is in conUict with a calcareous substnitum, sueh as an 

 egg-shell or a bone. On this point a num)>er of experiments 

 were conductdl by K. Lind (1.) with Asjteiyillus uiijei; I'tnicil- 

 liuin (jlawuiii, and JiufryttK nttt-mi. 



Of the organic substunces naturally forming such a ]Mirtitioii 

 wall, viz. either chitiu or cellulose, together with allied carbo- 

 hydrates, the first comes under consitleration in all cases where 

 the fungus endeavours t*j perforate the shell of an insect. In 

 order to elTect this it has need of an enzyme cajtable of dis- 

 solving chitin, on whith point several reports have been jnade 

 by Zoi'F (X.). However, even when the object infested with 

 the i«irasitic fungus is a fungus itself, the collaboration of 

 a similar enzyme is necessary, since chitin (.^ 226) forms ai 

 principal constituent of the membrane of many members of this 

 class. The faculty of excreting an enzyme capable of dissulving 

 cellulose and allied carbohydmtes liecomes maiidy apparent 

 when higher plants are infested by a fungus. The fijst notice 

 of the occurrence of such an enzyme in KiDinjii^tes was that of 

 DE Baky (II.) in 1SS6, in the case of Si-lnutiuia {I'l^iza) 

 Libert iana ; and a similar one was recorded in 1S8S by !M. 

 Wauu (I), in an allied species injurious to lilie.s. A year later, 

 E. Kissling found the same faculty in S<-lei<)/iuiu Fui-Lxliuna, 

 and this was confirmed by J. Behkexs (IV.), M. MiYosui (II.), 

 and M. NouuiiAisKN (I.). Subseijuently, on the basis of his own 

 experinu'iits, ^1. O. Ueixhakut (I.) came to the conclusion that 

 the mend)rane-di.s.solving enzyme secreted by the lir>t-named 

 iSrlerotinia is different from that of the second species. This is 

 by no means .surprising, in view of the great vaiiety of carbo- 

 hydrates (J^ 227) taking part in the stjucture of the vegetable 

 cell wall. The ability of liotri/iis cinena to secrete an enzyme 

 ciipable of dissolving true cellulose has been demonstiiited by an 

 experiment, carried out by J. Beuhexs (IX.) in a manner to 

 which no objection can l>e niised. On the other hand, J'vuiril- 

 liuin (jluuciim, 1\ luteuin, Jihir.ujnis ni'jru'aii.f, and probably also 

 Monilia fniclii/ena, have been proved incapable, though, with 

 the exception of the last-named species, they can attack the 

 so-called centnil lamella (.^ 119) and therefore .secrete a ptHrtin- 

 dissolving enzyme. Another organism capable of dissolving 

 true cellulose is the vine rt)ot mould, examined by J. Behkexs 

 (Xll.), and termed by him P.o.udoJhniatoj/iora. This is a 

 nou-^withogenic mould fungus occupying an unknown po.sitiuu 

 in the botanical .system; it grows generally on wood, and has a 

 particular atlinity for vine-wood, which it rots and destroys. 



Accordini: to C/atek (II.), the lignilied cell walls of higher 



