12 DIVISION 7. GENERAL MORPHOLOGY. 



Gastromycetes and Hymenomycetes (Polyporus, Thelephora, &c.), is often compara- 

 tively thick, and in an older state is not unfrequently much thickened, even to the 

 obliteration of the lumen. The cells for example of the pileus of Polyporus fomen- 

 tarius, of Crucibulum vulgare 1 and many other species, have in some parts the appearance 

 of solid cylinders, in others have a distinct cavity. The thickened membranes are 

 either firm and brittle or flexible, or gelatinous and soft. Where the thickening is 

 slight, as on the lateral walls of many Filamentous Fungi (Dematieae, Botrytis cinerea, 

 Peronospora), the membrane is usually homogeneous and not stratified, and even 

 the transverse walls are generally undivisible or with difficulty divisible into two 

 lamellae. But strongly thickened walls often show very distinct stratification without 

 as well as with the aid of reagents which cause swelling of their substance, such 

 as solution of potash or Schulze's solution or sulphuric acid. Good examples are the 

 thallus and gonidiophores of Cystopus, and the cells of the firm rind of the mycelial 

 strands of Agaricus melleus ; to these may be added the thickened membranes which 

 sometimes occur in Pilobolus in consequence of retarded growth (Coemans). The 

 membranes of many dry resting Fungus-tissues (Polyporus zonatus, P. versicolor, 

 Daedalea, Trametes Pini, Lenzites betulina, the stout hyphae of Thelephora hirsuta, 

 the threads of the capillitium of Bovista plumbea, Geaster, Tulostoma and many 

 others) often show at least two distinct layers, an outer and firmer one which is 

 frequently of a bright colour, and an inner softer and more transparent layer. 

 Further stratification cannot usually be detected in these cases even with the use 

 of artificial means such as boiling in potash, though they may be seen sometimes in 

 an older pileus of Polyporus officinalis. Here may be seen, when the plant is examined 

 in water, an outer thin and apparently firm layer, and an inner thicker and evidently 

 soft layer ; the outer layer is not sensibly altered when warmed in a solution of potash, 

 but the inner swells strongly, so as to protrude like a drop on the surface of fracture 

 beyond the outer layer, and at the same time often separates into numerous delicate 

 lamellae. 



Very beautiful stratification is also shown in the cells of many Fungi in which the 

 membrane is gelatinous and is capable of swelling strongly in water. In Geaster 

 hygrometricus the inner layer of the outer peridium, which bursts in a stellate manner, 

 consists of straight cell-rows of equal length closely packed together and standing 

 parallel to one another and perpendicularly to the outer layer ; they have a thick 

 membrane which is hard and cartilaginous in the dry state, but swells in water to 

 a tough gelatinous consistence and shows in a transverse section three to five lamellae 

 with different refringent power. The outermost lamellae of the cells in adjoining 

 rows are pressed close upon one another, and the bounding lines form a clearly 

 defined network on the transverse section. This structure is often obliterated in 

 old specimens. 



An exactly similar stratification to that which has been described in Geaster is 

 found in the tissue of Hysterangium clathroides 2 , which when dry is cartilaginous 

 but swells and becomes gelatinous in water, and also in the inner substance of many 

 sclerotia, as in the Sclerotinieae and in Typhula gyrans. 



The lower part, the stipe, of the branching body of Calocera viscosa consists of 

 rows of cells all running nearly parallel to the longitudinal axis of the Fungus. Thin 

 transverse sections through the stipe give therefore circular or polygonal sections 

 of the individual cells. The outermost of the three concentric layers of tissue which 

 compose the stipe is in the fresh state of a viscid gelatinous consistence, and is 

 formed of slender rows of thick-walled cells which appear 'at first sight to be imbedded 

 in a soft homogeneous jelly. But if thin cross sections of the dried stipe are allowed 

 to swell slowly in water, it becomes apparent in this case also that the jelly is formed 

 of as many gelatinous layers of membrane in close contact with one another at all 



1 Sachs in Bot. Ztg. 1855. * See Tulasne, Fungi hypogaei. 



