104 Journal op the Mitchell Society [August 



character of the peridium that in fresh plants before the collapse of 

 the threads in very old fruit-bodies is far from coriaceous; and the 

 rarity in which the rhizomorphous threads, or fibrils, run along and 

 cohere with the surface of the peridium, throw grave suspicion on the 

 position of this plant in the genus Rhizopogon. In this genus, how- 

 ever, the abundance and prominence of these fibrils varies greatly. 

 Zeller and Dodge (17) in their excellent monograph on Bhizopogon 

 include in that genus Bhizopogon maculatus Zeller & Dodge, a plant 

 with the outer peridium loosely woven. As the method of developing 

 the fruit-body in our plant is so different from anything we have 

 found described, it is quite likely that the plant belongs to an un- 

 described genus. Yet since so little is known of the development of 

 the other members of this group we have thought it best to describe 

 the plant as a species of Bhizopogon. 



Mycorhizal Character 



Quite a mass of literature has developed upon the subject of 

 mycorhizas since Frank's (5 & 6) excellent pioneer works on this 

 subject. He described mycorhizas on a number of plants, and de- 

 scribed the two types of mycorhizas: ectotrophic, or mycorhiza where 

 the fungal threads do not live within the host cells; and endotrophic 

 where the fungal threads do occupy the living host cells. He claimed 

 there was a symbiotic relation between the fungal threads and the host. 

 Even before Frank's papers Tulasne, as pointed out by MacDougal 

 (9), noted that Elaphornyces forms coatings on the roots of pine. Mac- 

 Dougal takes this reference from Tulasne 's Fungi Hypogaei, 1851. 

 We have not examined this edition; but in the edition of 1862 (15) 

 Tulasne does not name the pine as the host of Elaphornyces; but he 

 does have quite a discussion as to whether the Elaphomyces is parasitic 

 on the tree rootlets or whether, as Vittadini had suggested, the rootlets 

 profited by the presence of the fungus. He concludes that the para- 

 sitism of Elaphomyces is very problematical, if not improbable for 

 the greater number of them. Groom (7) showed that there is a 

 mutual exchange of material between the host and fungus in the 

 mycorhiza of Thismia, and claimed that the weight of evidence at that 

 time supported the sj^mbiotic view of mycorhizas as held by Frank, 

 but he says : ' ' Mycorhiza is, then, either a highly adapted and sym- 

 biotic community beneficial to both symbionts, or it is a pure matter 

 of infection of a plant by a fungus, and there is a constant struggle 



