So 



INTRODUCTION TO THE STUDY OF FUNGI 



of the stomata of the host-plant, where it becomes the new 

 mycelium of a spore-bed, which may either be that of a uredo- 

 spore or a teleutospore. 



The violet leaves which display on their under surface the 

 pale-brown scattered- pustules of the uredospores, will, later in 

 the season, exhibit also similar pustules mixed with them, and 

 nearly of the same size and form, but much darker in colour, or 

 the leaf may be occupied entirely with these darker pustules, 

 which contain the teleutospores. Seen under the microscope, 

 these spores of the third generation will be found to differ 

 from the aecidiospores and the uredospores in being two-celled 

 — that is to say, they are divided across the centre by a trans- 

 verse septum into two superimposed cells of a somewhat hemi- 

 spherical form, supported upon a 

 longer and more persistent hyaline 

 pedicel. They are produced, like 

 the uredospores, from a spore-bed 

 of mycelium arranged more or 

 less compactly side by side. The 

 apex of the upper cell has gener- 

 ally a more or less conspicuous 

 hyaline nipple in the centre. In 

 this species the coat of the spore 

 is smooth, but in some others it 

 is war ted or spinulose (Fig. 45). 

 The mature teleutospore may 

 germinate almost immediately, or 

 in some species only after a con- 

 siderable period of rest, in which latter case they are practically 

 resting spores. The germ tube from either cell, projecting through 

 the germ-pore, is at first a simple tube into which the contents 

 of the cell pass, and retreat to the upper end, which continues 

 to grow and become a promycelium. The extremity becomes 

 divided off from above downwards by one or more septa, and 

 then each compartment sends off a short pointed branch, which 

 is soon dilated at the point. This expanded end then assumes 

 an oval or kidney shape, and receives the contents of the com- 

 partment to which it belongs. In the course of a few hours 

 these new bodies are abstricted, and become promycelial spores. 



Fig. 45. — Germinating teleutospore 

 of Picccinia. After Tiilasne. 



