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INTRODUCTION TO THE STUDY OF FUNGI 



the upper portion of the columella. In the Stemoniteae the 

 typical genus is Sternonitis (Fig. 143), in 

 which the sporangia are free, whilst in the 

 other genera, as Amaurochaete, Brefeldia, 

 and Eeticularia, the sporangia are combined 

 into an aethalium. In the other section, 

 called Lamprodermeae, there are some half 

 dozen genera, in all of which the sporangia 

 are free, but in the most numerous and 

 typical genus, Zamproderma, the threads 

 of the capillitium arise from the abrupt apex 

 of a short columella. 



The third order is the Lithodermeae, 

 which includes a great number of species, 

 and is subdivided into two sections, in both 

 of which there is an external deposit of lime 

 on the wall of the sporangium. The 

 Bidymeae have a capillitium which is 

 wholly without lime (Fig. 144), and the 

 Physareae a capillitium which encloses lime. 

 We need not stay to analyse the different 

 genera in these two sections, inasmuch as 

 they will offer no difficulty to the student. 

 The Didymeae includes such genera 

 as Chondrioderma, Didymium, Lepidoderma, Spumaria, and 

 Diachaea (Fig. 145). In 

 Spumaria only are the spor- 

 angia combined in an aethal- 

 ium, in each of the other 

 genera they are free. The 

 typical genus, Didymium, has 

 the sporangium encrusted with 

 a powdery coating of lime, and 

 the distinguishing feature of 

 the three other genera consists in the coating of the sporangia. 

 The Physareae include eight genera, only one of which, Fuligo, 

 has the sporangia combined into an aethalium, as a generic 

 character, although in other genera some of the species 

 may form an aethalium. Physarum is a large genus in which 



FlQ. 143. — Sternonitis 

 fusca. 



Fig. 144. — Didymium farinacevm. 



