2i8 Transactions British Mycological Society. 



EXPLANATION OF PLATES XI AND XII. 



Fig. I. Horizontal view of mycorrhiza of Beech. 



Fig. 2. Horizontal view of mycorrhiza of Hornbeam. 



Fig. 3. Horizontal view of mycorrhiza of Sweet Chestnut. 



Fig. 4. Birch seedling; the entire root system is mycorrhizal. 



Fig. 5. Lower portion of the stipe of Amanita muscaria over the root of birch, 



showing hyphal connections between stipe, s, and mycorrhiza, m. 

 Fig. 6. Transverse section of mycorrhiza of birch, a, mantle; b, radially 



elongated cell of cortex; c, unmodified cells of cortex; d, endodermis; 



e, central axis, x 200. 

 Fig. 7. Portion of outer layers of the cortex showing vesicle (a) within the 



lumen of a cell. Hyphae from the inner layer of the mantle can be traced 



to a depth of three layers of the cortex, x 410. 

 Fig. 8. Portion of the mantle, m. x 410. 



THE LIFE HISTORY OF POLYTHRINCIUM 

 TRIFOLII KUNZE. 



(With Plate XIII.) 



By Jessie S. Bayliss-Elliott, D.Sc. and Olive P. Stansfield, M.Sc. 

 University of Birmingham. 



Polythrincium Trifolii, a Hyphomycete usually classified in 

 the Cladosporieae, has a cycle of development the knowledge 

 of which has, up to the present, been mainly a matter of con- 

 jecture. The fungus was described by Kunze (12) who remarked 

 at the end of his description: "Von einigen Botanikern erhielt 

 ich diesen, keinesweges seltenen, Pilz, fiir Sphaeria Trifolii P." 

 Persoon's description (13) of the latter is as follows: "Sphaeria 

 Trifolii: atra parva, magnitudine varia, cespitulo inaequah 

 ruguloso interne subpulverulento....Sphaerulae farctae, intus 

 albicantes." Fries (9) adds to Persoon's diagnosis that the peri- 

 thecia are immersed in stromata and suggests that the species 

 might better be placed in the genus Dothidea, a transference 

 which he afterwards made (10). Fuckel(ii) regarded these two 

 fungi as stages in the life cycle of an ascomycetous fungus which 

 he considered as a species of PhyUachora. "Fungus conidio- 

 phorus. Polythrincium Trifolii Kze.... Fungus spermogonium. 

 Sphaeria T. Pers. Dothidea T. Fr. Spermatiis minutissimis, 

 cylindraceis, curvatis, ascillantibus. Fungum ascophorum non- 

 dum vidi." Fuckel's name and the suggestion that these were 

 stages in the hfe cycle of the fungus have been generally adopted 

 in systematic works. In the present paper we are able to show 

 that there are three such stages but the perfect condition is not 

 a species of PhyUachora but of Dothidella. 



As far as we are aware the Pyrenomycete stage of this fungus 



