^^T-C'] Yates: HistoJogu of Califoiniian Jiolctaceae 225 



based upon natural affinities. In my (»\vn study of the histological 

 details of various North American species of Ceriomyces, differences 

 of seeming importance have been found between individuals which, in 

 other characters were apparently to he referred to the same species. 



I\rATERIAL 



The present study of the Boletaceae was started in the f.ill of 1912, 

 when individuals of three species were collected. Certain differences 

 noticed among indi\iduals apparently belonging to the same species and 

 discrepancies between the plants and the descriptions raised the ques- 

 tion whether .such plants were of different species, or forms of the same 

 species. The lack of agreement between certain of the plants and the 

 published descriptions presented the problem whether there might 

 not be distinct differences between our Californian plants and the 

 eastern representatives of the same species. For the purpose of com- 

 parison with our Californian plants, Dr. W. A. Murrill has very 

 kindly contributed several specimens of Eastern representatives pre- 

 sumably of the same species. 



In addition to the proposed study of histological details of the 

 various plants accessible, it was deemed desirable to make as detailed 

 a study as material and time would permit of the distribution of the 

 Boleti in California, particularly in the San P^'rancisco Bay region, 

 and of the seasons when the plants appear, habitat, economic import- 

 ance ; above all, a study of their histology to determine whether there 

 might be certain characters which would supplement the usual keys 

 and descriptions for the determination of dried material and even fur- 

 nish additional criteria for distinguishing the living plants. There is 

 frequently great difficulty in the determination of dried material due 

 to the fact that most of the species are determined in whole or in i)art 

 by color characters. For this reason the determination of dried speci- 

 mens often becomes quite impossible, especially if sufficient and exact 

 notes on the living material are lacking, as they usually are when the 

 plants have been collected by persons not familiar with this family. 



Since 1912 I have collected Boleti as opportunity offered and have 

 attempted to secure specimens of all the species growing in tlir S;ni 

 Francisco Bay region. This has been a somewhat difficult matter, 

 since most of these plants appear above the ground immediately after 

 the first rains in the fall, putrcly wilhiii two or three days and do ii<it 

 appear again until the t'olhiwing year. The only exceptions to this 

 rule seem to be Ceriomyces comDianis and h'ostliovitcs yraiuiIalKs. The 



