igi2] WOLF— ACTINONEMA ROSAE 225 



med 



in a radiating manner, especially noticeable at the margin of the 



shield, 

 walls. 



m 



shield varies in diameter 



more 



than one cell in thickness. In fig. 6 is shown a young stage 

 in the development of a perithecium. The shield forms a thin 

 layer above the epidermal cells or beneath the elevated cuticle. 

 Beneath the epidermal cells, and above the palisade parenchyma, 

 is an undifferentiated layer of fungous tissue, the stroma from 

 which the asci later arise. This stroma is 3-6 cells in thickness 

 and is mgjde up of cells similar to those of the shield. Occasional 

 filaments connect these two layers through the epidermal cells 

 of the host. In fig. 7, when the fertile layer has increased and 

 the fruit body has begun to be differentiated, the shield is still 

 distinct and not connected with it at the margin. At this time 

 the cells in the center of the young fertile stroma are thinner walled, 

 with a more deeply staining content. 



The asci are formed within the fertile stroma, arising from the 

 basal portion, as shown in figs. 8 and 9. In this way the cells in 



the 



formin 



covering over the hymenium. The development of the asci 

 within this fertile stroma is comparable with their origin in the 

 apothecia of the Phacidiales. The hymenium arises in the same 

 way, and the upper part of the stroma corresponds with the tissue 



hymenium before the opening of the apotheciu 

 is, however, this covering is not so well develop 



may 



opens. It may form a continuous delicate layer over the asci 



shield . 



mature 



.-> 



the 



hymenial layer. Fragments may 



the apothecium or they may disappear. It is only by the elonga- 

 ( n of the asci and the consequent increase of pressure that the 

 tide and shield, together with the upper part of the apothecium, 



manner 



/menium have ruptured 



11. 



