THE MYCELIUM OF THE FUNGUS. 35 



tho vegotative livphas which are usually found somowhat later among 

 the cells of the spongy parenchyma, ))el()W the vascular network. The 

 loss of chlorophyll from the two classes of leaf parenchyma connnonly 

 |)reserves the order here given. The form of the vegetative hyplue is 

 ver}' irregular, and their elements, or cell members, are often of dif- 

 ferent size, length, and shape. The cells vary greatly in diameter 

 from one end to the other, are frequently much curved and twisted, 

 and oftentimes appear triangular in cross section. The branches 

 nr.ay arise from greatly enlarged triangular ))ifurcations, or in other 

 instances directly from the sides of the cells. T'hese vegetative hj^phoe 

 are all intercellular so far as observed, but are commonly found adher- 

 ing closely to the cell walls of the host, frequently \vra[)ping about the 

 parenchyma cells. The walls of the hvphie are semitransparent but 

 tirm, commonly having a slight yellowish cast. The septa present 

 peculiar characters. Two adjoining cells of a hypha have the appear- 

 ance of being separately closed at the end and united with each other 

 by means of an intervening plate, which if it should he dissolved or 

 lost would leave the cells separated but closed. These peculiar septa are 

 remarkably refractive and characteristic. They ai"e well shown in the 

 drawings of Sadebeck (Die parasitischen Exoasceen, riam])urg, 1893, 

 Tal). II, tigs. 7, 8). The predominating characters of the vegetative 

 hypha? are shown in PI. II, tigs. 1 and 2, of this bulletin. The hyphae 

 there shown were carefully separated from the leaf parenc-hyma and 

 drawn under the camera. The vegetative hyphjB of the l)ranch are 

 much like those of the leaf, and have been seen most connnonly among 

 the looser parenchyma cells of the cortex just exterior to the bast fiber 

 bundles. Thus far they have never been found by the writer in the 

 cambial tissues. Sadebeck states that the m3'celium has been found in 

 the pith and medullary rays. 



The distributive hyphfe are shown in PI. II, tigs. 3, 4, and 5. 

 They have been found by the writer in the tissue lying close beneath 

 the epidermal cells of diseased peach twigs, and in great a))undance in 

 the pith. They are occasionally found in groups of several hyphje but 

 slightly separated from each other and following a course parallel to 

 the longitudinal axis of the shoot. The cells composing these hyphse 

 are much longer than either the vegetative or the fruiting forms, while 

 they are nearly straight and of more uniform diameter. The septa 

 are characteristic of those found in the other forms of the mycelium 

 of this fungus. Such distributive hyphas have been followed for some 

 little distance in the swollen portions of the peach twig, and the name 

 has been given them from their apparent function of spreading the 

 fungus in the branch. Such hypha^ l)ranch by bifurcation, the branches 

 commonly assuming a course parallel to the parent hypha and the 

 direction of the peach limb. 



