1912] WOLF— ACTINONEMA ROSAE 229 



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generic limits have been proposed. One finds included species 

 whose spores become brown, some which are aparaphysate, some 

 possessing filiform paraphyses, and others having paraphyses 

 which are enlarged at the tips. In fact, the whole family Micro- 

 thyriaceae is but little known, due in part to the fact that most 

 of the forms are tropical. A thorough investigation of perithecial 

 development is necessary, since very little attention has been 

 given to this group. The family is at present characterized by 

 having perithecia which are shield-shaped, thin membranaceous, 

 flat, with a rounded pore at the top and with a membrane formed 

 only on the upper side. With the exception of the species on rose 

 leaves, which I have studied, it is not known whether or not the 

 forms without an apical pore' possess one at maturity. It has 

 long been recognized, because of the entirely different manner of 

 development, that the Microthyriaceae are widely separated from 

 the other two families of the Perisporiales, the Erysiphaceae and 

 the Perisporiaceae. 



In order to see if other genera of the Microthyriaceae corre- 

 sponded in structure and development with the forms on rose 

 leaves several of them were examined. Asterina orbicularis B. & 

 C., n. 231 of Ravenel's collections, forms entirely superficial 

 perithecia, sending hyphae partially through the cuticle. Asterina 

 inquinans E. & E., n. 1785 N.A.F., is also superficial, ends of 

 the mycelium being observed in the stomata. Asterina plantaginis 



s, n. 791 N.A.F., forms spherical perithecia entirely sunken 

 within the host tissue. The perithecia are ostiolate and appear 

 to have the characters of a Sphaerella. Micro peltis longispora 

 Earle, n. 6349, plants of Porto Rico, is entirely superficial. Micro- 

 thyriutn littigiosum Sacc, collected at Frankfort, Germany, by 

 Dr. Paul Magnus, seems to form superficial perithecia, but the 

 mycelium is present in the epidermal cells. Myriocopron smilacis 

 (De Not.) Sacc, n. 600 E. & E., N.A.F., also forms superficial 

 perithecia and the mycelium occurs in the stomata. None of 

 these representative genera seem to be comparable to the type 

 of development as exhibited by the rose fungus. Since so little is 

 known of the perithecial development and the method of securing 

 food supply of the Microthyriaceae, this family would afford an 



Elli 



