MILDEWS AND RELATED FUNGI 1 65 



The apogamous formation of fruit also occurs in this suborder. The 

 asci are united into definite, usually fiat layers, which are in open 

 fruit bodies known as apothecia. Conidiospores are also found in 

 some of the forms and the conidiophores are of diverse character. 

 The asci are usually eight-spored. The fungi of this suborder are 

 either parasitic, or saprophytic in habit, and a few of the fleshy members 

 of the family Pezizace^ are edible. 



Family i. Hysteriace^e.^ — The apothecium is elongated and the 

 opening is a long wide cleft between the approaching walls of the 

 apothecium, so that the ascigeral layer is exposed at the time of the 

 spore discharge. 



Some species of the genera Lophodermium and Hypoderma are 

 dangerous parasites of leaves; for example, L. pinastri attacks pine 

 leaves; L. nervisequum attacks the spruce tree; while Hypoderma 

 hrachysporum is found on the white pine, Pinus strobus. Such genera 

 as Lophium, Hysterium, and Glonium include species which are sapro- 

 phytic on bark and wood. 



Family 2. PHACioiACEiE. — The apothecium is rounded, seldom 

 elongated and its walls are separated through a star-shaped opening, 

 rarely a cleft-like opening, so that the ascigeral layer is fully open at 

 maturity. The family includes such parasites as Nemacyclus niveus 

 on coniferous needles; Rhytisma acerinum, which produces black tar- 

 like blotches on maple leaves; and R. salicimim, which causes similar 

 black areas on willow leaves. Several species of Trochila are found 

 on the leaves of different plants. 



Family 3. Pyronemace^. — ^The fruit body is placed on fine 

 hyphge or on a felt-like cushion of hyphae. At first it is spheric; later, 

 it is flatly expanded. The hypothecium is occasionally feebly de- 

 veloped, at other times it is strongly so. The peridium is poorly formed, 

 or entirely absent. The most interesting genus is Pyronema. P. 

 confliiens has a fruit body i mm. across, and of a yellow or reddish 

 color. It is often found in spots where fires have been kindled in the 

 woods. The structure of the apothecium and the method of its forma- 

 tion following the sexual union of an antheridium and oogonium have 

 been described by Harper^ and the essential details have been given 

 on a former page of this book {ante^ pages 123 and 126). 



^ Harper, R. A. : Sexual Reproduction in Pyronema confluens and the Mor- 

 phology of the Ascocarp. Annals of Botany, 14: 231-400, 1900 



