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upper surface. When the leaf is cut across and the cut end is 
examined, these plates or lamellae appear as columns several cells 
high topped by a cell of special form. 
19. SPORE-CASE AND PERISTOME OF A Moss (Funaria 
hygrometrica). 
The mouth of the capsule or spore-case of most mosses is 
fringed with a series of teeth called the peristome. Under the 
influence of changing conditions of moisture the peristome exe- 
cutes movements which tend to open or close the orifice of the 
capsule and thus aid and regulate the scattering of the spores. 
20. Lip anp Rin oF a Moss Capsule (/unaria hygrometrica), 
The lid covers the orifice of the spore-case or capsule of the 
mosses. It falls off at maturity and permits the spores to escape. 
A ring of cells of peculiar form is usually developed around the 
usually separates from the adjacent tissues as a spiral band, or in 
fragments. 
21. PERISTOME OF A Moss (Muium cuspidatum). 
The capsule or spore-case of most mosses has at its orifice a 
structure called a peristome. This is usually consists of pointed 
appendages or teeth, which are hygroscopic, that is, they change 
in position with changes in the humidity of the air, and thus aid 
and regulate the dispersal of the spores or propagating bodies. 
22. Cross SECTION OF THE LEAF-STALK OF A FERN (Polypo- 
dium vulgare ). 
The external portion of the stalk is composed of very thick- 
walled cells, becoming thinner toward the center of the stem, 
where two bundles of vessels and fibers may be seen, surrounded 
by a brown sheath. 
23. SporE-Cases OF THE PoLypopy (Polypodinn: vulgare). 
The spore-cases of the ferns open along a line bounded by two 
cells of special form, known as the lip-cells. On the opposite 
