27 



Lime (calcium carbonate). This is present in all genera Nos. 

 1-8, Badhamia to Didymium inclusive. It may be in the stalk, 

 columella, peridium or capillitium; and in all but Didymium it 

 is in the form of minute, rounded granules. In Didymium it is in 

 crystals, usually in or on the sporangium-wall, and rarely else- 

 where. The lime may be recognized by crushing a sporangium 

 in water under a cover glass and observing it with the micro- 

 scope, when the countless hyaline or colored granules or crystals 

 will be seen among other parts of the sporangium. In lime-less 

 forms they are absent. Also, in some species not mentioned, the 

 lime may be in crystalline plates, rhombs, or irregular masses. 

 There is no lime in the remaining genera except occasionally 

 in certain species of Trichia and Perichaena, but there it may be 

 ignored as it is usually regarded as anomalous. With a little ex- 

 perience the student will be able to recognize the calcareous 

 genera — in fact any genus — as generic differences, together with 

 general appearance, are prominent enough to be noticed with 

 a hand lens. 



Capillitium. This is the system of threads within the spo- 

 rangium among which the spores are distributed. It is entirely 

 absent in Cribraria, Dictydium, and Ceratiomyxa. In Tubif- 

 era, Enteridium and Lycogala, there is no true capillitium but 

 the imperfect walls of the confluent sporangia are regarded as 

 a pseudo-capillitium. In all other genera mentioned there is a 

 true capillitium, the characters of which often make the generic 

 distinctions. 



Peridium. This is the wall of the sporangium enclosing the 

 spores and rupturing at maturity. It may consist of several 

 layers, firm or frail; and persistent for some time, or vanishing 

 rapidly after maturity. In aethalioid forms it is usually called 

 the cortex. 



Columella. That part of the stalk or an elongation thereof 

 extending into the sporangium; or, in sessile forms, a support- 

 ing structure for the capillitium arising within and from the 

 floor of the sporangium. 



Genus 1. BADHAMIA 



The genus is marked by the character of the capillitium 

 which is calcareous throughout. There is also lime in the 

 peridium. Stalks when present are rarely calcareous, and colu- 



