ASCOMYCETES 279 



the sycamore it is in one stage primarily a disease of the leaf 

 veins, although commonly the death of considerable portions of 

 the lamina adjacent soon follows. In another stage the fungus 

 is notably fatal to shoots, young trees, and seedlings. According 

 to Edgerton this fungus may produce in the early spring an 

 effect very similar to frost injury. Indeed, these injuries have 

 been referred by several to spring frosts. On the whole this is 

 one of the most disastrous anthracnose diseases known, and far 

 greater attention would be directed to it if greater concern were 

 felt for the sycamore, which is, nevertheless, a most important 

 shade tree. 



The fungus. The interesting life history of this fungus has 

 been carefully worked out. There are three types of imperfect 

 fungi as well as the ascigerous form in the life cycle of this organ- 

 ism. A typical Glceosporium stage (see Glceosporium) appears 

 upon the leaves, and the pustules or acervuli are well developed 

 upon the veins of both the upper and lower' surfaces. Upon 

 small, colorless conidiophores ovate conidia are produced measur- 

 ing 10-15 X 4-6^. The acervuli are from 100 to 300/* in diam- 

 eter, and the spores are produced in such quantity that in moist 

 weather they are forcibly ejected in creamy masses or strings. 

 This stage has long been known to mycologists as Glceosporium 

 nervisequum. Upon the twigs the size and type of acervulus has 

 caused the fungus to be referred to the form genus Myxosporium. 

 The further growth of the stroma later in the season may develop 

 the pycnidial or Sporonema stage, in which similar small conidio- 

 phores are developed from all sides of a more or less chambered 

 pycnidium. The ascigerous stage is abundantly developed on 

 affected leaves which have wintered over in the open. This stage 

 may appear either during late winter or early spring. The peri- 

 thecia vary greatly in size, but are ordinarily from 150 to 250/* 

 in diameter, with beak 50-100/1* long. The asci are, according to 

 Edgerton, 48-60 x 12-15^. They are broadly clavate and bent 

 at right angles near the base. The apex is thickened, and there 

 is a terminal pore surrounded by a more refractive ring. The 

 ascospores are invariably eight; they are hyaline, elliptical or 

 arcuate, once septate, and composed of a large upper cell and 

 a small lower. The germ tube emerges invariably from the larger 



