A NEW 8PECLES OF MULBERRY FUNGUS. 197 



almost every portion of the diseased roots, forming irregnlnr networks 

 of various complexity (PL. XXV, Fig. 4). They are ;^-l mm. thick 

 and of a purplish brown colour like the young pileus ; and as to tlieir 

 mode of ramification there seems to be no regularity. Without des- 

 troying even their finest brandies, they can be very easily detached, 

 with a needle, from the roots upon which they grow, t() a length 

 of several centimetres (PL. XXV, Fig. 5). They are often found 

 free, either forming large groups in spaces left between the partly 

 detached cork layers of old diseased roots, or solitarilv in the soil. 



The microscopical structure (jf the mycelial sti-and is ditferent 

 from that of Agaricus iiielleus, whose minute details are now well 

 known from the excellent description given by the late Prof. De 

 ßary.* Li the ])resent species the axial portion of the mycelial strand 

 consists of thick-walled hyplue, 3 U. in diameter, mixed with a few 

 finer ones ; and the peripheral portion consists entirely of finer hyplue 

 (VL, XXVI, Fig. 1). Ill the transverse section of the strand this is 

 more clearly seen (PL. XXVI, Fig. '2). In the mycelial strand of 

 Agaricat) vielleiis the hyjiliœ are so compactly arranged as to form a 

 tissue as is clearly seen in the cross section ; + but in the present 

 species the hyphas composing the strand are so loosely put together 

 that they easily separate from one another, and in the cross section 

 they present a circular and not angular form, since they are not 

 pressed together so as to assume the latter form. Moreover the form 

 of the cross section of the strand in Agaricus inellcas is round, but in 

 this species it is flattened. The thickening of the strand is ett'ected 

 either by the copious branching of a single hypha (.)r by the coales- 

 cence of two or more strands. In the group of hypha; formed by the 

 first method, there is always an axial or original thick hy[)lia 



* De Bary, Vergl. Morphol. u. Biol. d. Pilze ; Eng. traus. p. 2H-29 

 t See Fig. 11, p. 2t, of the baiue book. 



