ORDER HEMISPHAERIALES 293 



or subcuticular or which have a hypodermal stroma connected with an 

 epiphyllous stroma by strands of hyphae emerging through the stomata 

 or other openings. Asexual reproduction is known in a few forms and 

 consists of the formation of conidia from some of the external hyphae or 

 in pycnidial structures. With few exceptions the HI or more genera and 

 over 300 species are leaf parasites, largely tropical but represented in the 

 temperate zones by a number of genera. Arnaud (1930) has studied the 

 structures of many of these fungi, especially in relation to the host 

 tissues. 



Kilhan (1922) studied the sexual reproduction in Stigmatea rohertiani 

 Fr., a form previously included in the Family Mycosphaerellaceae of the 

 Sphaeriales. A subcuticular pseudoparenchymatous stromatic layer is 

 produced and in the thicker central portion of this appear several short 

 cells one of which becomes a binucleate oogone with a receptive papilla 

 and another a binucleate antherid. After the fusion of these cells there 

 follow several nuclear divisions and a fusion of male and female nuclei. 

 The resultant diploid nuclei pass out into the ascogenous hyphae which 

 give rise to asci arising from the floor of the ascocarp between the loose 

 stromatic hyphae. This hypothecial floor is pseudoparenchymatous and 

 the top is hemispherical, of radially arranged hyphae which break to leave 

 a central ostiole. Several functional oogones and antherids may be found 

 in each stroma as occurs in formation of the apothecium in Pyronema. 

 The aberrant nuclear behavior described by Killian suggests that this 

 process should be reinvestigated. 



Luttrell (1940) studied the reproduction in Morenoella quercina (Ell. 

 & Mart.) Theissen of the Family Microthyriaceae. This species grows on 

 the leaves of various species of oaks (Quercus). The mycelium is superficial 

 and forms a network of fine dark hyphae. By the division and radial 

 growth of several cells of a superficial hypha an elongated shield, one cell 

 in thickness, is produced. On the under side of this shield is developed a 

 plectenchymatous layer, two or three cells thick, of hyaline cells. In this 

 appear ascogenous hyphae of binucleate cells whose terminal cells become 

 the asci. As these enlarge the roof is broken open along a longitudinal 

 slit, and eventually the intervening stromatic tissues are destroyed so 

 that finally the asci stand side by side. While these ascocarps are develop- 

 ing circular spermogonia are produced, with a single top layer of dark 

 cells and a central ostiole and a floor of ovoid hyaline cells which break off 

 successively small rod-shaped spermatia. No union of these spermatia to 

 other cells was observed. 



Theissen and Sydow (1917) recognized five families in this order as 

 follows: 



Family Stigmateaceae. Upper surface of radially arranged hyphae, 

 arising subcuticularly, vegetative mycelium lacking or almost so. Eleven 

 genera of which Stigmatea is the type genus of the family. 



