64 FREDERICK A. WOLF 



* 



mesocarp and endocarp, are apparently alike. During ripening, 

 however, the cells of the endocarp do not become mushy or to 

 any marked degree deliquescent, while as a result of pectin diges- 

 tion the walls of the mesocarp become quite watery. The fact 

 that gum pockets are asymmetrical can not be considered as proof 

 either for or against the presence of cytase. 



The unilateral excretion of cytase in the production of gum- 

 mosis does not appear to present insurmountable difficulties, inex- 

 plicable by cytolytic activity nor is such a phenomenon at all 

 in opposition to other known cases. A most remarkable case of 

 unilateral diffusion and digestion by an enzyme occurs in Copri- 

 nus atramentarius.* Not only do the basidia undergo autodiges- 

 tion from below upwards on each gill, but each cystidium dis- 

 appears a few minutes before the basidia in its neighborhood come 

 to be involved within the upwardly progressing zone of spore dis- 

 charge. 



A further argument advanced by Butler against the hypothesis 

 of enzymotic hydrolysis is called forth because of the manner in 

 which he finds the cell-wall to be attacked. He reasons that the 

 enzyme "would have to attain the power of action only after 

 having diffused out into the secondary and primary lamellae, 

 thus only being able to attack the third membrane, which it 

 permeates, after having hydrolyzed the former and that in a cen- 

 tripetal manner. Such a mode of action would be indeed pecu- 

 liar." If the cell-wall, including the primary membrane, were 

 homogeneous in its chemical composition and only one enzyme 

 were operating, his position would be tenable. We know, how- 

 ever, that the wall is not homogeneous and that two or more 

 enzymes are necessary to its digestion. It has long been known 

 that there is a difference of composition of the middle lamella 

 and the secondary membrane. Payen 9 pointed out that the 

 middle lamella is composed, entirely or nearly so, of calcic pectate, 

 which opinion has been confirmed by Mangin. 9 Pectase, which 

 acts upon this substance, if secreted by the protoplast might per- 



8 Buller, A. H. R., The function and fate of the Cystidiaof Coprinus atramen- 

 tarius. Ann. Bot., 24: 613-629, pi. 50-51, 1910. 



9 Vide Green, Reynolds, Fermentation, p. 279. 



