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52 MISSOURI BOTANICAL GARDEN. 
indications in certain stems which were especially favorable 
for the purpose. There certainly is still much doubt 
whether all the stems having this cellulose layer do finally 
become wholly lignified, and this seems especially true of 
the Salicaceae. 
The exceptional cases mentioned above where the cellu- 
lose seemed to extend into the secondary layer (which is 
usually lignified), are not considered in this connection. 
Indeed they may very well be due to arrested development 
and are here so considered. 
DELIGNIFICATION BY FUNGI. 
Potter states that ‘‘ the conclusion is inevitable that the 
occurrence of cellulose which has been attributed to the 
action of the fungi must to some extent be ascribed to 
conditions already present,’’ implying that the cellulose 
which is found as a supernumerary lining layer of the 
wood fibers is the same cellulose which is found in woody 
tissues which are badly rotted by certain of the wood rot- 
ting fungi. He very evidently had in mind certain experi- 
ments of Ward* and Biffenf in testing the action of 
Stereum hirsutum and Bulgaria polymorpha upon wood 
when grown in pure cultures upon it. In both of these 
cases it happens that the delignification was apparently not 
very extensive and affected but a portion of the wall. In 
making the above statement Potter was at least partly 
correct in applying it to such cases, where the delignifica- 
tion was rather slight and affected but a portion of the wall. 
The statement should have been limited to such cases, as 
it is not applicable to those where the delignification has 
taken place throughout the whole wall as is the case in the 
last stages of disease caused by many of the wood rotting 
fungi, for the cellulose of normal wood occurs in such a 
® Ward. Phil. Trans. Royal Soc. 189. Series B. (1897). 
+ Biffen. Annals of Botany. 15:119-133. (1901.) 
