228 University of California Puhlications in Botany [Vol. 6 



oiighly investigated and their life-histories are not well known. In my 

 study the only plants not subject to the attacks of insect larvae were 

 Boletus luteus and one form of Ceriomyces communis. 



Technique 



In this study sections were secured and compared from both dried 

 and living material. The living material was cut into small pieces 

 and killed by placing in boiling water. This process was sufficient, 

 since sections showing nuclear behavior were not essential. After boil- 

 ing, the material was passed up through the alcohols to 95 per cent 

 to harden and dehydrate, and then down through the alcohols to pure 

 water again. It was then frozen in gum arable solution and the sections 

 cut on the rotary microtome (compare Osterhout, 1904). 



Section 25/x to 50/x in thickness were found to be the most satisfac- 

 tory for study. Sections thinner than this showed a tendency to fall 

 to pieces. 



Dried material was placed in cold water and then boiled for per- 

 haps ten minutes when glycerin was added to about one per cent. The 

 material was then allowed to cool in the water, which was later poured 

 off. The subsequent preparation of the material was after the same 

 fashion as in the case of the living specimens. 



Comparatively few sections of living material were cut and 

 mounted by the paraffin method, but they were so little superior for 

 the purpose of this study to those secured by freezing that the paraffin 

 method was discontinued. 



Flemming's triple stain was tried with the paraffin mounts but 

 with little success. Safranin and Delafield's haematoxylin were also 

 tried and both gave fairly satisfactory results. However, most of 

 the sections used in the study were not stained, as it was found that 

 practically as good detail could be secured without staining. The 

 greater portion of the work was done on unstained material ; observa- 

 tions were, however, checked up with material put through the staining 

 process. Except for certain purposes, the stained material presented 

 no decided advantages over the unstained. 



Structure 



Search of the literature fails to disclose any special papers on 

 the structure of the Boleti. A few scattered references in connection 

 with discussions of other problems give an idea of their structure in 



