DIDYMIUM.] 
DIDYMIACEJi). 
93 
Order II. — DiDYMiACEiE. Deposits of lime in crystals or 
crystalline discs distributed over the sporangium-wall ; capillitium 
without lime-knots ; sporangia simple, except in Spumaria, where 
they are combined into an sethalium. 
KEY TO THE GENERA OF DIDYMIACEM 
Lime-crystals stellate, distributed over the sporangium -wall. 
(12) DiDYMIUM. 
Fig. 20. — Didymimi effusum Link. 
a. Two sporangia, one entire, the other showing 
columella and capillitium. Magnified 12 
times. 
b. Capillitium and fragment of sporangium- 
wall, with crystals of calcium carbonate 
and two spores. Magnified 200 times. 
Fig. 20. 
Lime-crystals heaped together, at first concealing the confluent 
hollow sporangia. 
(13) Spumaria. 
Fig. 21. — Spumaria alba DO. 
a. ^thalium. Natural size. 
b. Capillitium and fragment of sporangium-wall, 
with crystals of calcium carbonate and 
two spores. Magnified 200 times. 
Lime-crystals lenticular, 
Fig. 21. 
n^.; fi,n ^^i^^^ ^ith radiating stri^, scattered 
over the sporangium- wall. 
(14) Lepidoderma. 
Fig. 22. — Lepidoderma tigrinum Eost. 
a. Sporangium. Magnified 6 times. 
b. Capillitium and spores. Magnified 140 times. 
Fig. 22. 
(1797). Sporangia stalked, sessile, or plasmodiocarps. not 
forming an ^thalium ; sporangium-wall membranous, besd. w^h 
