322 Bulletin 73. 



Hymeniiim. From the interior of the tissues the mycelium 

 grows to the surface and spreads, by branching, out over the epi- 

 dermal cells just beneath the cuticle. The cells of the subcutic- 

 ular layer soon become nearly isodiametric and are usually de- 

 veloped in such numbers that eventually they are closely crowded, 

 when they become angular in outline. By a less profuse develop- 

 ment they may appear as variously branched chains of oval cells. 

 These subcuticular cells are very rich in protoplasm, much more 

 so than the cells wit hin the tissue. They make up what is called 

 the hymenium. In figure 81 is shown a section of a portion of a 

 deformed bud of Pninus angustifolia presenting the intercellular- 

 mycelium and 5'oung hymenium of Exoascus mirabilis Atkinson. 

 In fig. 83 is represented a surface view of a portion of the hymen- 

 ium of the same species. 



Each of the cells of the h3^menium elongates perpendicularly to 

 the surface, forming C3dindrical or clavate cells which divide by a 

 septum into two cells, the septum usually being near the base. 

 The inner cell is the stalk cell while the outer cell is the ascus or 

 fruiting cell. In each ascus there are developed a variable num- 

 ber of spores, usually four or eight. These are rounded, oval, or 

 elliptical in form, and are colorless. At normal maturity a per- 

 foration usually occurs at the apex of the ascus and the spores are 

 ejected with considerable force. The ascus becomes turgescent 

 by endosmosis, this produces a pressure upon the walls and a 

 rupture occurs at the weakest point, which is at the apex. 

 De Bary* says that the ejection of the spores takes place in a 

 manner exactly similar to that in various species of other Dis- 

 comycetes which he examined. I have several times watched 

 under the microscope the expulsion of the spores of some of the 

 Discomycetes like Dasyscypha virginea (Batsch) Fuckel, Propolis 

 faginea (Schrad.) Karst. Trichopeziza capitata (Peck) Sacc, and 

 others. In the Pyrenomycetes I have watched the same phenom- 

 enon in the case of Spherella pyri Auersw. By mounting speci- 

 mens which are not too old in fresh water and immediately noting 

 the asci under the microscope they can be seen to become turges- 



* Exoascus pruni und die Taschen oder Narren der Pflaumenbaume, Beit- 

 rage z. Morph. u. Phys. d. Pilze, Erst. Reihe. Abgedruck. a. d. Abhandl. d. 

 Senkenb. Naturf. Gesellsch, Bd. V, pp. 183 and 184, Frankfurt, 1886. 



