PUCCINIA. 333 



outwards, arise from the mycelium, which from their swollen 

 ends abstrict a unicellular spore, the uredospore. The surface 

 is ruptured, its edges thrown up laterally. The spores are in 

 different stages of development. Those that are ripe appear 

 an elongated oval, and with sufficiently strong magnification 

 we can distinguish two layers in their wall. The outer, dark 

 brown, is covered with numerous small warts ; the inner, less 

 dark, shows several, usually four, regularly-distributed pits in the 

 equator. The contents of the spore are granular, in the interior 

 parts a lively orange-red. 



Cross-sections through the haulm of oat, bearing the dark- 

 brown streaks of teleutospores, show the same structure, as far 

 as the hyphae are concerned, as we have already seen.' The 

 teleutospores are mounted upon stalks similar to those of the 

 uredospores, but thicker walled. The teleutospores are two- 

 celled. The two cells together form an obovate body, somewhat 

 tapering at its two ends, and with a dark-brown wall. I Plants 

 examined in the course of the summer may have uredo- and 

 teleutospores simultaneously in the streak. 



We may add that these teleutospores hibernate, and are, 

 therefore, of the nature of resting-spores ; and are first capable 

 of further development in the next spring. Each of the two cells 

 puts out a delicate germ-tube, the so-called promycelium, which 

 at its upper end cuts off four cells ; each of these puts forth a 

 short awl-shaped outgrowth, which cuts off at its apex a kidney- 

 shaped sporidium, | These sporidia can only infect, i.e., germi- 

 nate upon, the Barberry leaf ; if they happen upon a sufficiently 

 young leaf, their germ-tube pierces .straight through the outer 

 wall of the epidermal cell directly into the interior of the host. 

 As we therefore see, the way through the stomata, by which the 

 germ-tubes of the aecidio- and uredospores enter, is not the only 

 one by which infection is possible. 



The various structures met with in the life history of Puccinia 

 yraminis may be further illustrated by the subjoined figure, the 

 description of which may be compared with the text. 



Reproduction of a Hymenomyceie, Russula. In order to study 

 the structure of the hymenium of the Hymenomycetes, it is 

 preferable to use one of the numerous species of Toadstools 

 (Amanita), Mushrooms (Agaricus-Psalliota), or Russula. We 

 will select a Russula, because this possesses cystidia "also. The 

 cap or pileus shows on the under side radially-arranged lamellae 



