266 BOTANICAL GAZETTE [march 



artificially at Lafayette, he was unable to get any seed. H. Dalyi, 

 according to Farwell, is a variety of H. Maximiliani, related to it 

 much as var. oppositifolius Farwell is related to H. giganteus. An effort 

 should be made, however, to raise a giganteusY. Maximiliani hybrid. 

 H. amhiguus (Gray) Britton is supposed to be a hybrid giganteusX 

 divaricatus, or at any rate to have giganteus as one parent. Thellung 

 records a garden hybrid laeiiJlorusXrigidus, and the plant called H. 

 serotinus Tausch (i 828) is supposed to be strumosus X rigidus. Evidently 

 there is a great deal to be done, both in the field and in the garden, before 

 we can reach a fairly clear understanding of this subject. It seems 

 possible that in this genus the origin, through hybridization, of distinct 

 plants, with the attributes of species, may be demonstrated. — T. D. A. 

 CocKERELL, University of Colorado, Boidder, Colo. 



RELATIONSHIPS WITHIN THE RHODOSPOREAE 



During the last 15 or 20 years the author has studied the structure of 

 30 to 40 species of Pluteus and 4 or 5 species of Volvaria. In all of these 

 species, without a single exception, the trama of the lamellae presents a 

 curious and interesting structure. In the majority of the Agaricaceae, 

 the trama hyphae of the lamellae lie, in general, in a parallel direction, . 

 as in Mycena, Tricholoma, Collybia, Inocybe, Entoloma, Leptonia, etc. 

 In Russula and Lactarius many of the cells are so swollen that the 

 trama of the lamellae presents a vesiculose appearance. In Amanita 

 the hyphae show a strong divergence from the median plane toward 

 the subhymenium as they descend in the trama. 



In Pluteus and Volvaria, on the other hand, the most prominent 

 hyphae converge as they descend in the trama of the lamellae. Along 

 the median plane of the lamella there can usually be seen, in section, a 

 layer of hyphae (sometimes more slender) against which these prominent 

 cells converge. Attention was called to this peculiar structure in 

 Pluteus seticeps in 1902,^ but no interpretation was offered as to its 

 origin or significance. 



During the summer of 191 7, Professor Leva B. Walker, of the 

 University of Nebraska, while studying the development of Pluteus 



^ See Leptonia seticeps Atkinson, Jour. Myc. 8:116. 1902. Further collections 

 and studies of this species show that it is a Pluteus. While the gills are attached to the 

 stem before the expansion of the plant, they become free, rounded behind, and distant 

 from the stipe. The stipe also easily separates from the pileus, and other structural 

 characters are clearly those of Pluteus. It is therefore Pluteus seticeps Atkinson, ined. 



