270 COMPARATIVE MORPHOLOGY OF FUNGI 



separate pycnidia like M . Hippocastani, and Guignardia Aesculi (Stewart, 

 1916), which in the United States causes leaf blotch of horse chestnut as 

 M. Hippocastani in Europe. Dilophia graminis is regarded as the perfect 

 form of Dilophospora graminis which causes the Dilophospora disease of 

 wheat. Sphaerulina intermixta is saprophytic on dry branches on roses 

 and blackberries and S. Trifolii, the Sphaerulina leaf spot of clover. In 

 S. intermixta, Brefeld (1891) reports that the hyaline ascospores may 

 develop, immediately after ejaculation, to a sprout mycelium (Fig. 

 179, 2) which under certain conditions swells into an amorphous cell 

 clump (Fig. 179, 4). The same sprout cells may also be cut off by the 

 hyphae. After exhaustion of the nutrient solution, the sprout cells 

 change into bi- or multicellular gemmae which, under certain conditions, 

 develop to long, brown chains at times intertwined to papery membranes 

 (Fig. 179, 6). Their ability to germinate is not injured by drying and is 

 retained more than 1^ years. Under normal conditions, they germinate 

 to a hyaline sprout mycelium or with germ tubes. This type of germina- 

 tion has not been reported elsewhere in the group and probably was 

 based on impure cultures. 



Cytologically, in contrast to the previous families, there is a large 

 amount of investigation in the Mycosphaerellaceae. Higgins (1914, 

 1920) investigated M. (Septorisphaerella) nigerristigma, on leaves of 

 Prunus pennsylvanica and M . (Ra?nularisphaerella) Bolleana on leaves 

 of Ficus carica, and found in them, as in Polystigma, a helical ascogonium 

 with a functionless trichogyne. Killian and Likhite (1923) and Likhite 

 (1926) in a species on Salix caprea (judging from the figures, probably 

 Mycosphaerella with the imperfect form described as Hendersonia foliorum) 

 have observed that the helical ascogonium, as in Polystigma, is divided 

 into a sterile basal and a fertile apical, multinucleate portion. Degener- 

 ation of sterile and fertile portions proceeds until only one or two cells 

 remain, from which ascogenous hyphae develop in the usual manner. 



Finally Killian (1917) has reported still functional antheridia in 

 Venturia inaequalis. As this species has been investigated more fully, 

 its life cycle is given in detail. Its mycelium lives between epidermis 

 and cuticle in the leaves of the apple. The formation of brown conidio- 

 phores (Fusicladium dendriticum) ruptures the cuticle and finally peels it 

 off. Thereby the transpiration of the cells beneath increases, and they 

 dry out. The fungus begins to grow during the summer, and forms a 

 small, brown, round, woolly covering with characteristic dendritic indenta- 

 tions. In the fall the mycelium in the older middle part of the cover 

 begins to die off. In this spot the injured leaf surface is discolored and 

 gray. The leaves are scurfy, yellow and fall off early in October before 

 the healthy ones. 



In the peripheral parts, the ageing hyphae remain alive and grow to a 

 plectenchymatic tissue. In November, when the leaf is entirely dead and 



