332 XXIV. REPRODUCTION OF THE HIGHER FUNGI AND LICHENS. 



sterigmata, abstrict at their points exceedingly small, globular 

 cells, the spermatia, which are evacuated from the organ in a 

 mass of slime. The sterigmata themselves contain orange-red 

 oil drops, which give to the entire organ, especially in its outer 

 parts, its special colour. The spermatia do not germinate ; their 

 significance is still unknown. There has been a disposition to 

 take them for male sexual products, and to consider that the 

 sexual act leads to the formation of the aecidium fruits. 



As already mentioned, the fungus lives as a second generation 

 upon Gramineae, It belongs to the hetercecious parasites, which, 

 in contradistinction to the autcecious, go through their alter- 

 nation of generation upon different hosts. This has been demon- 

 strated by direct sowing of the aecidium spores upon seedlings of 

 the cereals. The uredo condition of Puccinia graminis we 

 encounter not infrequently in corn fields, from mid-June to 

 autumn,, upon rye > wheat, barley, oats, and especially on the 

 couch-grass or twitch (Triticwn repens). It is found chiefly 

 on the haulm and the leaf-sheaths of the infected plants, and 

 Os easily recognised as narrow, rust-coloured to dark-brown 

 streaks, running parallel with the veins. Upon the leaf-sheaths 

 and haulm (stem) these streaks attain to even two or more 

 inches in length. The epidermis of the host is torn open and 

 raised by the protruding gonidial tissue. First appear the rust- 

 coloured patches of the summer spores, the uredo-spores, with 

 which are gradually associated brown winter spores, teleuto- 

 spores. These usurp the place of the uredospores, and at length 

 completely supplant them, whereon the patch becomes dark- 

 brown, almost black. Towards the end of summer only teleuto- 

 spores are to be found. 



If fresh material is not obtainable, that preserved in alcohol, 

 and even dry plants, softened in water, will serve for study. We 

 first prepare a cross-section through the haulm of an oat which 

 is infected with rusty uredo-streaks. We can easily demonstrate 

 upon the cross-section that the fungal hyphae only traverse 

 definite tissues of the host, viz., the chlorophyll-containing, 

 looser strips of tissue, which alternate with sclerenchymatous 

 strips in the periphery of the stem, and are covered with an 

 epidermis provided with stomata. Here the cells are densely 

 enveloped in hyphae, and their contents disorganised. In the 

 places where the section has passed through a uredo-streak 

 we can see numerous short and delicate branches, directed 



