136 FIRST GROUP. THALLOPHYTES. 



their appearance as longitudinal projections on the inner (under) surface of the pileus. 

 On the surface of the lamellae are the extremities of hyphal filaments, arranged 

 regularly like a palisade, and perpendicularly to the middle, radially-disposed hyphae, 

 of which they are the branches, These palisade-cells form the hymenium ; the basidia 

 with the spores proceed from them, but the basidia are not all fertile ; the larger number 

 are sterile paraphyses, and some which swell up into a spherical form are distinguished 

 as cystidia. The basidia are usually cylindrical, and four new growing-points, the 

 sterigmata, appear simultaneously on the apex of each ; thesterigmata elongate a little and 

 then terminate in a fine needle-point, which swells into a small globe and as it enlarges 

 becomes ovoid in shape. The contents of the basidia pass into the swollen part, which 

 is then separated off from the sterigma by a dividing-wall, and the spore is formed. 

 Meanwhile all parts of the pileus have expanded, and its superficial cells have become 

 thickened to form an outer coat. Then follows a rapid development of the stipe ; the 

 pileus is raised higher into the air, its tissues expand, and it discharges its spores. 



Some further mention may be made here of Brefeld's interesting experiments. He 

 showed that if the fructifications that are beginning to form on the sclerotia are 

 removed, new ones are formed on them in almost unlimited numbers. If the pileus is 

 removed in a young fructification, a new rudimentary fructification is formed by 

 vegetative growth on the cut surface of the stalk from any of the superficial cells, and 

 unites without break of continuity with the old stump and developes perfectly upon it. 

 ' Every cell of the vegetatively produced fructification, every cell of the stipe, every 

 hypha of the pileus, of the lamellae, of the hymenium has the power of growing out into 

 a fructification.' In the same way young fructifications, if detached and placed in a 

 nutrient solution, grow out into mycelial filaments, and pieces cut out of older 

 fructifications will do the same. The germination of the sclerotia is materially promoted 

 by light. The development of the pileus is hindered by darkness, but the stipe attains 

 a considerable length. 



It appears then that the sclerotia of Coprinus stercorarius are resting states of the 

 mycelium, and pass immediately after their formation into a state of rest. It is 

 otherwise with the Rhizomorphae which are the sclerotia of Agaricus melleus. These 

 are root-like branched structures composed of strands of mycelial filaments, which 

 are parasitic on the pine and give rise there to peculiar formations (' Harzsticke '), as 

 Hartig has shown 1 . Hartig was the first to discover that Rhizomorpha belonged to 

 Agaricus melleus^ and his statements have been since confirmed and supplemented by 

 Brefeld. The formation of the Rhizomorphae on the mycelium produced by the 

 germination of the spores of Agaricus melleus begins in the same way as that of 

 sclerotia of Coprinus stercorarius. But the Rhizomorphae do not pass at once into the 

 resting stage ; they are sclerotia with growing-points, and consist of a brown rind 

 surrounding an internal mass of tissue in parts not in contact with a nourishing 

 substance. The apex of the sclerotial strand is its growing-point, inside which new 

 formations take place, and consists of extremely small cells connected together without 

 interstices and perfectly alike at the summit of the growing-point, though the existence 

 at this point of a true tissue cannot be certainly proved. The Rhizomorphae have been 

 seen making their way into the pine. If the species lives beneath the bark (Rh. 

 subcorticalis), its rind does not turn brown, the constituent elements multiply in- 

 definitely at its circumference, and hence it attains a considerable thickness and an 

 indefinite breadth. It remains plastic, altering its form at pleasure at any point, being 

 sometimes thin as a needle, sometimes of enormous thickness, sometimes round, 

 sometimes flat. With the extinction of the growing-point the Rhizomorphae enter upon 

 the true sclerotial condition. The fructifications of Agaricus melleus are developed 

 directly from the Rhizomorphae. A number of the inner hyphae begin to sprout, 

 break through the rind, and commence the formation of the fructification. 



\ R. Hartig, Wichtige Krankheiten d. Waldbaume, Berlin 1874. 



