DIDYMIUM.] 



DIDYMIACE-E. 



93 



Order II. — Dibymiace^. Deposits of lime in crystals or 

 crystalline discs distributed over the sporangium-wall ; capillitium 

 without lime-knots ; sporangia simple, except in Spwma/ria, where 

 they are combined into an sethalium. 



KEY TO THE GENEEA OF DIDYMIAGE^. 

 Lime-crystals stellate, distributed over the sporangium-wall. 



(12) DiDYMIUM. 



Fig. 20. — Bidymium effwum Link. 



a. Two sporangia, one entire, the other showing 



colnmella 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 sporangiar. 



(13) Spumaria. 



Fig. 21. — Spumaria alia DC. 



a. -Sthalium. Natural size. 



J. Capillitium and fragment of sporangium- wall, 

 with crystals of calcium carbonate and 

 two spores. Magnified 200 times. 



Fig. 21. 



Lime-crystals lenticular, marked with radiating striae, scattered 

 over the sporangium-wall. 



(14) Lepidoderma. 



Fig. 22. — Lepidoderma tigrinvm, Eost. 

 a. Sporangium. Magnified 6 times. 

 l. Capillitium and spores. Magnified 140 times. 



Fig. 22. 



Genus 12.— DIDYMIUM Schrader, Nov. Gen. Plant., p. 20 

 (1797). Sporangia stalked, sessile, or plasmodiocarps, not 

 forming an sethalium ; sporangium- wall membranous, beset with 



