348 H. MARSHALL WARD. 



crease and spread, and the leaf becomes sickly or " diseased," 

 and soon ceases to be of use to the plant. 



If the black, cloudy mottling just described be examined 

 with a good hand lens, or with a low power of the compound 

 microscope, it is seen to consist of aggregations of dense 

 black maculae, united by networks of fine and beautifully 

 branched dark lines. In some cases the whole surface of 

 the leaf is thus covered ; in others, the cloudy patches and 

 networks are confined to particular areas. Closer exami- 

 nation shows that the denser and blacker spots consist 

 of certain orbicular, boss-like bodies, from which the deli- 

 cate branched network spreads in a more or less stellate 

 manner, running into similar radiations from neighbouring 

 bosses, by branchings and anastomoses of all degrees of 

 complexity. 



If the epidermis of the leaf, together with the reticula- 

 tions, &c., described above, be carefully removed with a 

 sharp razor, and examined by transmitted light, their several 

 characters are determined still more easily; the deep, 

 shining black colour, however, being softened to a rich 

 vandyke-brown, tinged with olive. {Cf. fig. 2.) 



Still closer investigation, with a higher power, shows that 

 the dark bosses (which are of various sizes, from that of a 

 small dot to the diameter of a small pin head) are closed 

 and appear nearly homogeneous when young, but become open 

 above by irregular radiating slits as they increase towards 

 maturity, and disclose a cavity within the boss, from which 

 spring masses of slender filaments and very delicate asci, 

 containing ascospores, the whole embedded in a sort of 

 gelatinous matrix (figs. 3 and 4). The networks of radiating, 

 branching, and anastomosing filaments, also, are now seen to 

 be composed of tubular and septate fungus-hyphse, the thick 

 walls of the long cells being strongly carbonised, rendering 

 them — as also those composing the ascus-containing bosses 

 — brittle and dark coloured. Here and there, united by 

 slender stalks to the deep-coloured hyphse of the network, 

 may be seen peculiar hyaline and colourless Haustoria, 

 dipping into the epidermal cells of the subjacent leaf (figs. 6 

 and 8), and anchoring the whole firmly thereon. 



For the sake of simplicity and clearness, I propose to 

 alter somewhat the order in which the following facts 

 became discovered, and to describe the anatomy and deve- 

 lopment of this fungus systematically, from the germination 

 of the ascospore on the young leaf in the rainy season. 



The spore itself is a short, cylindrical, deep brown body, 

 equally rounded at both ends, and slightly constricted in the 



