THE FUNGI 



179 



the generic name, Roestelia. The wall of the secidium is very much 

 developed, and finally protrudes as a long tube (Fig. 144, D). The 

 aecidiospores are carried back to the Cedar, and infect it afresh. 



Wheat-rust. Heteroecism was first observed in one of the Wheat- 

 rusts (Puccinia graminis) whose aecidia are produced upon species of 

 Berberis. Upon the Wheat two sorts of spores are borne, the red- 

 rust, or uredospores, long-stalked unicellular spores (143, D), and 

 the black-rust, or teleutospores. The former appear first, and. germi- 

 nate promptly, entering the young leaves through the epidermal cells, 

 and rapidly spreading the rust. The teleutospores appear later, 

 generally upon the stalks. These remain dormant during the winter 

 as black spots upon the stubble, forming the next season the sporidia, 

 which in the spring infect the young Barberry leaves. 



The commonest species of Wheat-rust in the United States is 

 Puccinia rubigo-vera, which is universally distributed. This species 

 forms its aecidia upon various members of the Borage family, e.g. 

 Hound' s-tongue (Cynoglossum), but the infection of the wheat is 

 mainly due to the uredospores developed from the mycelium 

 which has passed the winter within the wheat-plant often the 

 "volunteer wheat," or possibly 

 other Grasses. 



The Auriculariaceae 



This is a small family of which 

 the best known is the genus 

 Auricularia, which develops con- 

 spicuous ear-shaped fruit-bodies 

 upon rotten wood. The spores 

 in these forms are borne upon 

 jointed basidia, much like those 

 of the Rusts. 



Order II. Tremellinese 



The Tremellinese resemble the 

 Auricularinese in having the basi- 

 dia divided, but in these the divi- 

 sion is longitudinal, the spores 

 being formed upon very long 

 sterigmata, which are in twos 

 or fours, resulting from the split- FIG. 145. ^, Tremellasp., the gelatinous 

 ting of the primary basidium fruit-body attached to a dead twig. 

 CFiff 145^ Various sneoies of (Natural size.) B, conidia, con, and 



basidiospores, sp, of T. lutescens ( X400) . 

 Iremella are common upon dead (B, after BREFELD.) 



