336 Notes on Parasitic Ascomycetes. [Sess. 



of any apical pore or opening for the escape of the 

 spores, and consequently the latter are liberated by the 

 irregular rupturing or final decay of the perithecia them- 

 selves. The Perisporiacese are divided into two groups — 

 viz., (first) the Erysiphese, which have a white or pale- 

 brownish mycelium, as well as hyaline and non-septate or 

 continuous spores ; and (secondly) the Perisporieae, which 

 have a dark-brown or black mycelium. In some species 

 of the latter the spores are hyaline, in others brown, and in 

 others variously septate. Of the Erysiphese, 6 genera — 

 Podosphcera, Sphoerotheca, Phyllactiniaj Uncinula, Microsphcera, 

 and Erysiphe — have to be mentioned ; while those of the 

 Perisporiese calling for notice are 3 in number — viz., 

 Meliola, Asterina, and Capnodium. These 9 genera may 

 conveniently be referred to in the order stated. 



In Podosphcera each perithecium contains a single ascus, 

 and the latter contains 8 spores. Each perithecium is fur- 

 nished, either at its equatorial or apical region, with ap- 

 pendages which are forked at the tip. The most common 

 species is P. oxyacanthce De Bary, which in its conidial state 

 is often so abundant on young twigs and leaves of hawthorn 

 bushes as to impart to the hedges an appearance of having 

 recently been sprinkled with whitewash. The perithecia, 

 however, are by no means very freely produced, and should be 

 looked for in late autumn. 



Another species, P. tridactyla^ De Bary, occurs on leaves of 

 wild and cultivated species of Prunus in some districts ; while 

 another, P. myrtillina (Schubert) De Bary, is developed on the 

 under surface of blaeberry leaves. The latter species is rare 

 in Britain, where it is apparently confined to Scotland. It 

 has occurred in several parts of the Highlands, and at Currie 

 Glen, near Borthwick Castle, Mid-Lothian, where it was found 

 at an excursion of the Society last October.^ 



In the genus Sphcerotheca, each perithecium contains a single 

 ascus, and the latter contains 8 spores. The appendages 

 are filamentous, unbranched at their apex, attached to the base 

 of the perithecia, and often interwoven with the mycelium. 

 The most notable species are S. pannosa (Wallr.) L^v., S. Cas- 



1 It has more recently (Sept. 1911) been discovered near Moffat, Dum- 

 friesshire. 



