uo 



ASCOMYCETES. 



cell-nucleus. This tissue so formed may be compared to the 

 nutritive tissue formed secondarily from parenchyma as a result 

 of other fungoid diseases, <\g. in violas attacked by Uroci/sfis 

 violac. If the formation of sporangia ensues in parts which 

 would normally become collenchyma, the tissues there remain 

 thin-walled. 



The sporangia of Protomyccs, according to De Bary/ begin to 

 develop as soon as the young leaves and shoots of the host- 

 plants emerge above the ground in spring. The sporangia first 



Fig. iT. — Protomyces macrosporus. Section through swollen leaf-stalk oi Aego- 

 potUuni. Towards the right end the cells are normal, elsewhere they are, under 

 the influence of the mycelium, much enlarged and secondarily divided ; two 

 roundish sporangia lie in tliis tissue, (v. Tubeuf del.) 



appear as series of swellings on the hyphae and are easily 

 detected in deformed plants as large thick-walled bodies lying 

 in the intercellular spaces. They are liberated on decay of the 

 host-plant, and in spring the contents swell up so as to rupture 

 the thick outer wall, and the endosporium emerges as a vesicle 

 or sporangium into which the protoplasmic contents pass to 

 form numerous rod-shaped spores. The spores are ultimately 

 expelled with considerable force, and, after conjugating in couples, 

 they send forth a germ-tube which penetrates again into the 

 tissues of the host-plant. 



' De Bary, Beitrciffe z. Morph. n. Physiol, d. Pike, also Botan. Zeitumj, 1874. 



