BASIDIOMYCETES 



405 



sive change of form and often with loss of individuality to form fructifi- 

 cations, tissues and organs which in their structure and functions are 

 specialized like those of the Cormophyta. All these tissue-like hyphal 

 systems (plectenchyma, etc.) which have grown from the original, uni- 

 form, secondary mycelium are called tertiary mycelia, and develop either 

 as rhizomorphs and sclerotia or as fructifications. 



The mycelial threads develop in connection with fructification and 

 sclerotial formation. Their existence may be easily understood, from an 

 anthropocentric point of view, by considering that an enormous store of 



G, Gj Fj Gs 



♦ ♦-Hm-* 



Fig. 268. — Mcrulius lacrymans. 1. Portion from mycelial strand. 2. Section of 

 fructification. H, ordinary vegetative hyphae; Fi to F 3 , developmental stages of filamen- 

 tous hyphae; Gi to Gt, developmental stages of vascular hyphae; G 5 , degenerating hypha; 

 Hm, hymenium; Tr, trama. (1 X 240; 2 X 120; after Falck, 1912.) 



nutrient is necessary in order to develop in a short time the large and 

 complex structure which we call the mushroom. The ordinary vegeta- 

 tive hyphae with their clamp connections would hardly be adapted to 

 rapid translocation. At the base of the fructification, mycelial threads of 

 variable thickness, originally formed of a few hyphae, penetrate further 

 into the ground, and gradually fuse with other threads to larger structures. 

 Their anatomical and ontogenetic relationships are still little known. 

 By the investigations of Falck (1909, 1912) on Lenzites and Merulius, it 

 was shown that in these two genera the original, central hyphae have 

 largely disappeared and new hyphal systems, "vascular" hyphae and 

 " fibre" hyphae, are formed whose structure and grouping are character- 



