Nature and development of plants . picuous outgrowth from the mycelium called the stroma(Figs. 150; 152, D). The majority of the genera are saprophyticupon dead and decaying vegetation, though some of them aredestructive parasites. The black knot, Plowrightia, the cause ofa serious disease to plum and cherry trees, illustrates very wellthe characteristics of this order. The mycelium grows in the 2l6 OPEN TYPE OF ASCOCARPS cambium and cortical regions of the branches, causing the barkto split open in the spring when spore bearing hyphae extendup into the air forming velvety coating (Fig. 150, c
Nature and development of plants . picuous outgrowth from the mycelium called the stroma(Figs. 150; 152, D). The majority of the genera are saprophyticupon dead and decaying vegetation, though some of them aredestructive parasites. The black knot, Plowrightia, the cause ofa serious disease to plum and cherry trees, illustrates very wellthe characteristics of this order. The mycelium grows in the 2l6 OPEN TYPE OF ASCOCARPS cambium and cortical regions of the branches, causing the barkto split open in the spring when spore bearing hyphae extendup into the air forming velvety coating (Fig. 150, c). By theapproach of winter, this mycelium has grown into the familiarblack knotty mass in which are developed numerous ascocarp-like bodies (Fig. 150, as). The spores from these ascocarps arecarried by the wind in the early spring to other branches andprobably infect the budding trees. Other conspicuous forms areXylaria and Daldinia, which develop an extensive stroma onstumps and trees that contains numerous ascocarps (Fig. 152).. Fig. 152. Other common forms of the Spheriales: A, habit of Hysterio-graphium on a dead twig. B, ascocarps enlarged. C, ascus enlarged,showing character of ascospores. D, Daldinia. E, section of the same,showing that the stroma forms a concentric stratum of ascocarps, as. eachyear. F, Xylaria. G, the same with branch cut off to show the layer ofascocarps on the periphery of the stroma. In Hypoxylon, the stroma containing the ascocarps breaks throughthe bark of a large variety of trees and shrubs in the form ofspherical or cake-like masses (Fig. 149)- 89. Order f. Hypocreales.—These fungi are distinguishedfrom the Sphaeriales by their rather fleshy or membranous as-cocarps and stroma, which range in color from white to yellow, DEVELOPMENT OF PLANTS 217 purple, scarlet and brown. Numerous species are saprophyticwhile others are parasitic upon higher plants, fungi and is a common example of this group causing the disease
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