THE MYCETOZOA 



53 



and covered with minute spines or tubercles. The spores are ap- 

 proximately spherical, and 9 to 12 yu. in diameter. In several species 



the spore -wall has been found to 

 give the reaction of cellulose. 



Fio. 11. 



Tart of a section through a young 

 sporangium of Trichia varia, showing 

 the division of the nuclei prior to 

 spore - formation. x 650. c, capil- 

 litium thread ; n, a nucleus. In 

 several cases the axis of the dividing 

 nucleus is directed towards us, and 

 the karyokinetic figure is therefore 

 not displayed. 



Part of a section through a spor- 

 angium of Trichia raria after the 

 spores are formed. Capillitium 

 threads are seen in longitudinal and 

 transverse section, x 650. 



The ripe sporangium thus consists of a mass of spores, 

 enveloped by the sporangium wall and traversed by a supporting 

 reticulate capillitium, which, like the wall, has a dry membranous 

 character, though charged throughout with white granules of lime. 

 As ripening proceeds the sporangium wall becomes more and more 

 friable, until it breaks and the spores are spread abroad on the 

 lightest currents of air. 



Considerable variations of structure are presented by the 

 sporangia of the Mycetozoa. The stalk may be absent altogether, 

 the sporangia being sessile on the substratum (Fig. 13, e). When 

 present it is usually solid, but may be hollow, and sometimes, as in 

 Trichia fallax, may contain cellular elements, which appear to be 

 aborted spores. 



In many species the stalk is continued in the interior of the 

 sporangium as a structure known as the columella, which may reach 

 to the apex or terminate short of it. A columella may, however, 

 be present in sessile sporangia, as in species of Chondrioderma 

 (Fig. 13, e}. 



Stalked sporangia are, at their first formation, sessile, and in 

 the majority of cases the stalk may be regarded as the basal part 

 of the sporangium wall, which has shrunk and fallen in about the 

 base of the sporangium, as the latter has risen above the substratum 

 (Figs. 13, a, and 15, a) ; but in the Stemonitaceae the stalk, with its 



