[Vol. 2 



686 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



the growing margins of mature specimens where it is evident 

 that no mature basidia have yet been formed. 



Neither can these structures be regarded as paraphyses 

 that have become elongated and, therefore, more conspicuous. 

 While there may be no ground for the belief that paraphyses 

 can not assume such a form, yet there is no evidence to indi- 

 cate that conspicuous sterile structures ever have arisen in 

 such a manner. Moreover, the distribution of these struc- 

 tures under consideration makes impossible any such idea, 

 as they are scattered promiscuously and do not alternate with 

 the basidia. 



These two species then are to be distinguished only by their 

 habitat, and the size and shape of the pileus. In my own col- 

 lecting experience the former character alone is enough to 

 separate them, but when once the two plants are learned, the 

 matter of form and size will usually be sufficient for the 

 identification of the specimens, even if the habitat be unknown. 



As stated above, the hymenium of P. abietinus may at times 

 be lamellate. This statement is made only after a careful 

 study of the facts in the case. They are as follows : There is 

 a plant with apparently the same distribution as P. abietinus, 

 in which the hymenium is entirely lamellate. No exactly 

 intermediate conditions have ever been seen by the writer, 

 though he has collected both forms in Colorado. In all other 

 characters the two plants are precisely similar. The host is 

 always the wood of coniferous trees ; the pubescence and color- 

 ation of the pileus is the same; the spores and cystidia are 

 similar ; and the hymenium often has the violaceous tint char- 

 acteristic of P. abietinus. Irpex fuscoviolaceus is in all prob- 

 ability only another form of the same plant, although I have 

 never seen specimens of that species with the well-marked 

 lamellate hymenium of this form. The illustration (pi. 23 

 fig. 1) is from specimens communicated by Prof. C. R. Orton, 

 of State College, Pennsylvania. He writes that the rot pro- 

 duced by this fungus is almost identical with the one produced 

 by P. abietinus. Patouillard 1 represents the cystidia of Irpex 



1 Hym. Eur. pi. 3. f. 23. 1887. 



