CAPSULAR FUNGI— PYRENOMYCETES 



199 



tiated into chains of hyaline conidia, which fall away and are 

 capable of germinating and producing a new mycelium. In 

 this condition the parasite is a mould, 

 or Hyphomycete, and was formerly in- 

 cluded under the geniis Oidium, under 

 the supposition that it was a complete 

 and autonomous Fungus. Eecent in- 

 vestigation has shown that this stage of 



mould is Only the COnidial condition of Fig. 87. — Perithecium and 



some species of the Erysipheae, which ^ ™ th s P oridia of 

 succeed the Oidium. In the first in- 

 stance minute spherical yellow bodies appear on the surface of 

 the mycelium, and these gradually enlarge until they become 

 just visible to the naked eye, and acquire a dark brown colour 

 (Fig. 87). These are the perithecia, or 

 membranaceous capsules, attached at the 

 base by a copious mycelium and surrounded 

 by a circlet of free arms, or processes, as 

 appendages, which vary in the different 

 genera. In Erysiphe they are thread-like 

 and fiexuous, of equal diameter throughout, 

 and simple. In Uncinula the arms are 

 hooked or curved at the tips (Fig. 8 8). In 

 Phyllactinia the appendages are straight, and often inflated at 

 the base. In Sphaerotheca they are fiexuous and sometimes 

 vaguely branched. In Podosphaera the 

 appendages are repeatedly forked at the 

 tips, as they are also in Microsphaera 

 (Fig. 89). Internally these globose 

 perithecia are replete with the ascigerous 

 fructification. The asei are nearly 

 globose, or pear-shaped, and contain 

 hyaline elliptic sporidia. In Podosphaera 

 and Sphaerotheca each perithecium en- 

 closes but a single ascus. In the other 

 genera the asci are numerous in each perithecium. The 

 number of sporidia in each ascus varies with the genera, 

 but with the exception of a single genus these sporidia are 

 ovoid and continuous. In the exceptional genus Saccardia 



Uncinula. 



