MYXOGASTRALES ! 5 ! 



18. Capillitium forming an interior net-work of larger meshes and a super- 



ficial net- work of smaller ones. STEMONITIS. 



Capillitium forming only an interior net- work, and reaching the wall of 

 the sporangium with numerous free extremities. COMATRICHA. 



19. Plasmodiocarp laterally compressed, splitting into two valves. 



ANGIORIDIUM. 

 Plasmodiocarp terete, elongate, opening irregularly. CIENKOWSKIA. 



20. Capillitium wanting. 21. 

 Capillitium present. 25. 



21. Wall of sporangium of uniform texture, or wanting entirely. 22. 

 Wall of sporangium with net-like thickenings on the inside forming a 



sieve-like apparatus by the falling away of the outer layer. 24. 



22. Sporangia joined into a flat aethallium, their walls reduced to tri- 

 angular threads at the six angles of the united sporangia. 



CLATHROPTYCHIUM. 



Sporangia either growing singly, usually irregular in shape, or crowded 

 together , [but not forming an aethallium. 23. 



23. Sporangia grown together nearly their entire length, usually raised on 



a strongly developed stem-like hypothallus. TUBULINA. 



Sporangia usually of irregular shape, or regular, single or clustered. 



LlCEA. 



24. Thickenings of parallel ribs connected by much more slender trans- 



verse branches. DlCTYDiUM. 



Thickenings of net- work thin fibers with enlarged knots. CRIBRARIA. 



25. Sporangia or aethallia with columellae. 26. 

 Sporangia or aethallia without columellae. 27. 



26. Sporangia crowded on a well-developed hypothajlus. SiPHOPTYCHiUM. 

 Sporangia forming an aethallium with a thick bark. RETICULARIA. 



27. Capillitium with irregular or indefinite markings ; sporangia sessile 



with thick brown walls. 28. 



Capillitium with regular and definite thickenings in the form of warts, 



spines, rings or reticulations. 29. 



Capillitium with regular and definite thickenings in the form of spirals 



turning to the right. 32. 



28. Plasmodium forming roundish or hexagonal sporangia, opening in a 



circumscissile manner. PERICHAENA. 



Plasmodium forming a more or less elongate, bent and flexuous plas- 



modiocarp which is irregularly dehiscent. OPHIOTHECA. 



29. Sporangia enlarged (0.5-2 cm. in diameter), resembling small puff- 



balls, with a cortex of colored cells. LYCOGALA. 



Sporangia simple, small. 30. 



