234 BOTANICAL GAZETTE [September 



be loosened, and can be floated away, thus proving beyond a doubt that this 

 structure is wholly superficial and not subcuticular. Asterella rubi, therefore, 

 conforms to the present concept of the genus Asterella, but is of an entirely 

 different generic type from that represented by Diplocarpon rosae. 



EXPLANATION OF PLATE XIII 



Fig. i. — Acervulus of conidial stage (Actinonema rosae), with a section 

 of one of the radiating strands at the right of the acervulus; X400. 



Fig. 2. — Conidia formed free in culture; the two halves are easily sepa- 

 rable; germination of the separated cells; X400. 



Fig. 3. — Normal conidia from acervuli, and their method of germina- 

 tion; X400. 



Fig. 4. — Surface view of Diplocarpon rosae, showing the shield and sub- 

 cuticular strands from which it developed; X no. 



Fig. 5. — Surface view of mature perithecia in which the shield has been 

 ruptured irregularly and folded back; X55. 



Fig. 6. — A very young stage in the development of a fruit body in which 

 the shield and the stroma from which the asci are formed are distinct; C, 

 cuticle; B, epidermal cells; D, ascogenous stroma; X200. 



Fig. 7.— A stage in which the fruiting part of the perithecium has begun 

 to be differentiated; the shield and ascogenous stroma are separate; A, young 

 apothecium; X200. 



Fig. 8. — Differentiation of the asci within the apothecium; X200. 



Fig. 9. — Perithecium in which the epidermal cells still persist between the 

 apothecium and shield; the thin- walled cells of the upper part of the apothe- 

 cium form a covering over the hymenium; X 200. 



Fig. 10. — Perithecium in about the same stage of development as fig. 9, 



but the shield and fertile stroma are completely united; X 200. 



Fig. 1 1 .—Perithecium which is nearly mature; the hymenial covering 

 has broken; A, upper part of apothecium; B, shield; C, cuticle; E, epidermal 

 cells; X200. 



Fig. 12. — Mature fruit body of Diplocarpon rosae; some of the cells of 

 the upper part of the apothecium persist at the margin; X200. 



Fig. 13. — An old acervulus persisting at the side of a perithecium; X 200. 



Fig. 14. — A large disciform perithecium; some asci are mature and in 

 others the spores have not yet been formed; the ascogenous stroma and shield 

 have grown together and the epidermal cells have been destroyed; X 200. 



Fig. 1 5. — Section through a mature perithecium, showing the manner in 

 which the shield is folded back ; X200. 



Fig. 16. — Mature asci and paraphyses; the spores have been discharged 

 apically from one ascus; X400. 



Fig. 17. — Ascospores of Diplocarpon rosae; X400. 



Fig. 18. — Germination of ascospores; X400. 



