32 DIVISION I. — GENERAL MORPHOLOGY. 



to be spikey ; it often appears along the veins of the leaf, but always outside the 

 wood-bundles. I found the sclerotia of P. Candolleana on oak-leaves, but there also 

 only in the parenchyma. But the sclerotium of a small Peziza which inhabits the 

 leaves of Prunus insinuates itself among all the elements of the veins of the leaf. 



b. The structure of the sclerotia of several of the Hymenomycetes, especially Agaricus 

 cirrhatus, P. (?), A. tuberosus, Bull., and Hypochnus centrifugus, Tul., differs 

 little from that of the first type. The chief difference is that the cell-walls in the rind 

 are not a dark but a yellow brown ; the surface of the rind is in most cases tolerably 

 smooth, but in Hypochnus centrifugus it is uneven or felted over with the remains of 

 the hyphae which surround the sclerotium in its younger state. The hyphae of 

 the medullary tissue and their membranes are of varying thickness according 

 to the species ; they are in most cases chiefly filled with a watery fluid or with 

 air ; in Hypochnus centrifugus they contain drops of oil. I have never found 

 tissue-elements of the host enclosed in the medulla even of those of the above 

 mentioned sclerotia, which had developed in the interior of decomposing parts of plants 

 (Mushrooms). 



c. A somewhat different structure from the above is seen in a sclerotium in 

 Rabenhorst's Herb, mycol. Nr. 1791, incorrectly named Sclerotium stercorarium, and 

 of doubtful origin. Its white medullary tissue consists of thin-walled cylindrical 

 hyphae which contain a watery fluid, and are usually rather loosely interwoven, 

 the interstices being filled with air. Towards the surface the medulla passes gradually 

 into an outer covering of many layers of narrower hyphae, which mostly run parallel 

 to the periphery and form a tissue without interstices. The inner layers of this 

 tissue are colourless, towards the outside the membranes become gradually yellow- 

 brown, and those of the outermost layers are so considerally thickened that the lumina 

 are much reduced in size. The whole sclerotium is thus surrounded by a firm uneven 

 rind composed of several layers. 



d. The light-yellow Sclerotium muscorum, which also belongs to some Agaric, 

 consists of a web of broad thin-walled hyphae with narrow interstices containing air. 

 The hyphae, which are not arranged in any order, are composed partly of elongated 

 cylindrical and partly of short vesicular cells. The latter contain a clouded homo- 

 geneous yellowish protoplasm, or a watery fluid in which drops of yellow oil are 

 suspended. The surface of the sclerotium appears to the naked eye of a darker 

 colour than the centre, but under the microscope the structure is seen to be the 

 same throughout, and the medulla and rind are not clearly distinguished. Single 

 surface-cells project here and there as cylindrical papillae. 



e. The snow-white medulla of the sclerotium of Coprinus stercorarius, Fr. has 

 a similar structure to that in Sclerotium muscorum. It is a pseudo-parenchyma 

 composed of broad irregularly roundish or elongate-ovoid cells and single cylindrical 

 hyphae ; all the cells are very thin-walled and filled with a colourless, uniformly 

 and finely granular, somewhat strongly refractive protoplasmic substance, which issues 

 forth from injured cells and spreads through water and makes it turbid. These 

 cells form a close tissue which is hard in the dry state, and has more or less 

 narrow interstices filled with air. The cells of the medulla become suddenly smaller 

 towards the circumference. The surface of the sclerotium is formed of a firm 

 apparently black rind which is wrinkled in the dry state. Where this rind borders on the 

 medulla it shows four or five irregular layers of small cells of the shape and size of the 

 outermost cells of the medulla, but with brown membranes and apparently always 

 clear watery contents. This layer is surrounded by the more superficial rind 

 consisting of three or more layers of large cells usually of irregular roundish outline, 

 which at the periphery have some resemblance to the largest of the cells of the medulla, 

 and contain a watery fluid or air within a slightly thickened wall of a dark violet-black 

 colour. Many of the superficial cells of the rind project irregularly above the rest 



