BOTANY 



are the most important, and have the greatest number of species, while 

 the second, third, and fourth orders include only a few forms. 



Order 1. Uredineae (Rust Fungi) 



The Fungi of this order are all injurious parasites. Their mycelium lives in 

 the intercellular spaces in the tissues of the higher plants, particularly in the 

 leaves, which then acquire a spotted, rusty appearance. The Rust Fungi are 

 closely allied to the Brand Fungi. Like them, they produce chlamydospores 

 which break through the tissue of the host and form the rust spots characteristic 

 of these Fungi. The germ-tube resulting from the germination of a chlamydospore 

 gives rise directly to a transversely septate basidium (Fig. 286, A), from which 

 four sterigmata, each with a spore, are successively developed. Formerly it was 

 customary to designate the transversely divided basidium a promycelium, and the 

 basidiospores sporidia. The process of chlamydospore-formation, as exhibited by 

 the Uredineae, undergoes extensive and complicated modifications ; very frequently 



Fig. 287. — Puccinia fasca on Anemone nemorosa. Section through an jecidium ; h, tissue of inter- 

 woven, sterile hyphaj ; s, chains of spores ; p, peridium. (After v. Tavel, x 150.) 



three distinct forms of chlamydospores are produced by the same Fungus, at the 

 same time or in succession. 



1. The teleutospores (winter spores) which, as typical chlamydospores, prob- 

 ably constitute the original form of spores peculiar to all the species, are invested 

 with a thick wall. They are formed at the ends of numerous, closely-clustered 

 mycelial hyphfe which rupture the epidermis in small, usually more or less round 

 spots. They are frequently joined together in rows of two or more (Fig. 288, 1, 5, t), 

 and are produced in late summer, toward the close of the vegetative period. They 

 function generally as resting spores, and after hibernating, germinate in the spring 

 and develop at onee basidia, bearing four spores. 



2. The UEEDOSPOKES (summer spores) arise in the same or similar positions to 

 the teleutospores, but precede them in development. They germinate immediately 

 after their dissemination, producing a vegetative mycelium, and provide for the 

 multiplication of the Fungus during the summer. They are unicellular and 

 enveloped only with a thin wall (Fig. 288, 5 and 6). 



3. The .scidiospores, which are produced, prior to either of the other two 



