THALLOPHYTES 



89 



so into the basidiospores, have all been observed in mushrooms. In the common 

 field mushroom (Agaricus campestris) the basidium often produces only two 

 sterigmata and spores, but in such 

 cases four nuclei have been ob- 

 served in the mature basidium. 

 The vegetative mycelium has been 

 observed to be binucleate, the con- 

 dition found in the uredospore- 

 teleutospore mycelium of rusts. 

 With a uninucleate basidiospore 

 and a binucleate mycelium, it is a 

 matter of interest to determine 

 where the binucleate condition 

 originates. It is suggested that 

 the basidiospore upon germination 

 becomes binucleate. In that case, 

 if the interpretation applied to the 

 rusts (see p. 84) obtains among 

 the mushrooms, the mycelium with 

 its sporophore is the sporophyte, 

 and the basidiospore represents 

 the gametophyte. 





Fig. 200. — Coprinus : section of under side 

 of pileus, showing section of the stipe in the cen- 

 ter, and the radiating (sometimes branching) gills 

 coated by the hymenium. 



2. Gastcromycctcs 



These are the most highly 

 organized of the fungi, the complexity appearing in the structure of 

 the sporophore. The hymenium is inclosed within the sporophore, 



which opens only after the spores 

 are mature. The sporophore is 

 differentiated into an outer zone 

 of cortical hyphae {peridium) and 

 an inner mass of tissue (gleba) 

 which contains the numerous ba- 

 sidium-bearing chambers. These 

 chambers either are filled with 

 loosely woven hyphae whose lat- 

 eral branches terminate in basidia, 

 or are lined by a definite hyme- 

 Fio. ,0,.- Coprinus: section of the nial layer. The gradually increas- 



hymenium, showing basidia bearing basidio- ing Complexity of the sporophore 



spores; tin curving of the basidia makes it wi „ , je b serve( l i n the following 

 impossible to show their actual connections 



in a section. groups: 



