144 LEVINE: CyTOLOGY OF HYMENOMYCETES 
nature and function of the cystidium, and Buller and Knoll have 
ascribed to them hitherto unsuspected functions. Buller (1910) 
as a result of elaborate studies concluded that the cystidia of the 
Coprini act as props and emphasizes the importance of the inter- 
lamellar spaces for the dispersal of the spores. In Inocybe astero- 
phora Buller describes the cystidia as excreting a ‘mucilaginous 
substance. Patouillard (1887), Massee (1887, 1894, 1904, 1906), 
Istvanfhi (1896), Topin (1901), Maire (1910), and Demelius 
(1911, 1912) hold that the cystidia are organs of excretion or are 
in some way related to the functions of excretion. Maire (1910) 
holds with Topin (1901) that the function of the cystidium varies 
with the stage of its development. In its young stage the cystid- 
ium is a storage organ of reserve food for the hymenium. Ulti- 
mately the cystidium becomes an excretory organ. Massee 
(1887) holds that the cystidia of the gill-bearing fungi are the 
terminal cells of laticiferous vessels. Their contents escape 
through a nipple-like filiform attentuation at the apex of the 
cystidium. Miss Demelius (1911, 1912) is of the opinion that 
the cystidia serve to protect the fungus from the invasion of 
insects. She emphasizes their variability in form, as in Collybia 
radicata, which has spherical, spindle-shaped and finger-like cystidia 
upon which excretion products may or may not appear. 
' Knoll (1912) endeavors to prove that the cystidia are one- 
celled hydathodes comparable to the active water-excreting cells 
in the epidermis of the phanerogams. He maintains that trichom- 
hydathodes, as he calls them, are also found on all parts of the 
carpophore as well as in the hymenium. They are definitely 
shaped cells having a slender foot and a much expanded middle 
region while the upper part forms a sort of neck. The excretion 
forms a spherical drop at the apex. The fluid excreted contains 
a jelly which remains after the water has evaporated. Besides 
water, Knoll believes that the. cystidia excrete by-products of 
metabolism and so accounts for the appearance of crystals of 
calcium oxalate on their tops. He also holds that the hydathodes 
may have a protective function in the case of fungi with exposed 
hymenial surfaces. For Knoll, the cystidia of the Coprini are 
aberrant types whose true function remains obscure. 
