556 



COMPARATIVE MORPHOLOGY OF FUNGI 



called peridium for short. A further development in breadth is unknown 

 in them ; in many cases, however, no sharp difference between caeoma and 

 aecidium can be drawn, for there also appear in groups with well- 

 developed peridia, species with peridia rudimentary or almost lacking. 

 The development of the caeoma will be first described, e.g., Phrag- 

 midium violaceum (Blackman, 1904; Welsford, 1915), P. speciosum 

 (Christman, 1905), P. disciflorum (P. subcorticium) (Mme. Moreau, 1914) 

 Gymnoconia Peckiana (Christman, 1905; Olive, 1908; Kursanov, 1910), 

 Melampsora Rostrupi (Blackman and Eraser, 1906), M. Lini (Fromme, 



Fig. 373. — Phragmidium disciflorum. 1, 2. Development of caeoma. St. Z., sterile cells; 

 F.Z., fertile cells. (1 X 535; 2 X 670; after Moreau, 1914.) 



1912) and M. reticulata (Lindfors, 1924). The first indication of the 

 fundament consists in an accumulation of intercellular hyphae between 

 the epidermis and mesophyll. The cells of the hyphal knot next the 

 epidermis elongate perpendicularly to it and lie close together, forming a 

 subepidermal palisade layer. Each divides into a small sterile cell above 

 and a large fertile cell below (Fig. 373). Where there is enough room, 

 e.g., in the spaces between the epidermal cells, the fertile cell repeats this 

 division, so that a chain of as many as four sterile cells may result; in 

 Melampsora Lini there are usually two, and in Melampsora Rostrupi 

 many sterile cells. The nucleus of the sterile cell remains small, degener- 

 ates and disappears. This is followed by the gradual degeneration of the 

 sterile cells themselves. 



Meanwhile, proceeding from the middle toward the margin, the walls 

 between two fertile cells dissolve, the protoplasts fuse and a large, binu- 



