12 DIVISION I. —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! 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?, 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 
fotmed 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. 
