CHAPTER II. — DIFFERENTIATION OF THE THALLUS — MYCELIAL STRANDS. 2J 



the cushion, and breaking through the rind of the parent-strand grows in the manner 

 which has already been described. Its final medullary hyphae become continuous 

 with those of the medulla of the parent-strand. Schmitz first observed that, at 

 least when old strands are cultivated in a damp chamber, the place of every future 

 branch is indicated some days before its emergence by the appearance of a floccose 

 tuft of hyphae ^— i mm. in size, arising partly beneath, partly also according to 

 Hartig out of the surface of the parent-strand, which decays and disappears as 

 the branch is formed. 



The stronger subcortical strands and the membrane-like expansions in the 

 living tree are said by Hartig to be similar to the subterranean ones just described in 

 structure and development, except in respect 

 of certain differences arising from difference 

 of form, the somewhat smaller masses of 

 tissue, and the fainter tinge of brown on 

 the outer layers of the rind or the entire 

 absence of that colour. Very delicate myce- 

 lial membranes and slender tufts of ramifying 

 branches, which frequently arise on the edge 

 of the larger mycelial body, have a more 

 simple structure and consist only of hyphae 

 of the rind. There is one important pecu- 

 liarity in all these strands and expansions, 

 that the numerous hyphae which stand out 

 like hairs from the surface force their way 

 into the tissue of the rind and wood, and 

 spread and ramify there, and are organs by 

 which the Fungus takes up its food. They 

 often form bladder-like swellings in the 

 tracheides of the pine-wood which they 

 decompose, reminding one of the inner 

 layers of the rind of the strand, and their 

 number in the tracheides may be so large 

 as to fill them with a tissue of bladder-like 

 cells 1 . 



Brefeld has completed our knowledge of 

 the life-history of the mycelium of Agaricus 

 melleus by growing it from spores in an artificial nutrient solution (decoction 

 of plums). A delicate branched radiating primary mycelial hypha was developed 

 in about eight days from the germ-tube which issued from the spore cultivated 

 on a microscopic slide. Thick tuft-like branchlets from single branches of the 

 hyphae or from several adjacent ones then appeared in the centre of the circular 

 expansion which was some millimetres in size; these tufts raised themselves erect 

 and became united together into clews as large, according to the figures, as a 

 good-sized pin's head, after the manner of the sclerotia to be described below in 



Fig. 12. AgaricitsmclUus. Subterranean mycelial strand. 

 Isolated pieces of the large-celled originally axile tissue a — a, 

 from which the definitive medullary hyphae b grow as 

 branches. Magn. 390 times. 



1 R. Hartig, Die Zersetzungserscheinungen d. Holzes, p. 59. 



