200 Transactions British Mycological Society. 



Fig. lo. Stage showing the development of trabeculae. Spores are present 

 on many of these, borne on scattered basidia. A well-defined sterile base 

 is present, x 20. 



Fig. II. Slightly later stage, showing commencement of secondary growth in 

 thickness of the trabeculae. Note that the columella has almost dis- 

 appeared. X 12. 



Fig. 12. Not quite median section through the stage in which secondary growth 

 of the trabeculae is well advanced. Hymenium is now present, fig. 5 being 

 a drawing from this section, x 10. 



Fig. 13. Section through a plant shortly after commencement of the third or 

 peripheral stage of growth. The trabeculae are already gelatinised, the 

 peridium well defined and the hymenium at the stage shown in fig. 6. The 

 larger trabeculae persist as the veins shown in fig. 8, left, x 6 



STRAINS OF RHIZOCTONIA SOLANI KUHN 

 (CORTICIUM VAGUM BERK. AND CURT.). 



By H. R. Briton-Jones, B.Sc, D.I.C., A.R.C.S., 



University of Bristol Agricultural and Horticultural Research 



Station, Long Ashton. 



Introduction. 



During the course of work in Egypt in connection with the 

 "Sore-Shin" disease of cotton seedhngs caused by Rhizoctonia 

 Solani Kiihn, the fungus was induced under experimental con- 

 ditions to produce its fertile stage Corticium vaguni Berk. & Curt. 

 On comparing the R. Solani from cotton in Egypt with isolations 

 of the same species from other countries it was observed that 

 there were considerable differences between them in culture. 

 Duggar (i) had previously noted such differences and stated that 

 "in general it is felt that these differences are such as might be 

 due to permanent differences in the pathological strains, on 

 the one hand, or may be regarded as temporary differences due 

 to recent environment on the other." In order to ascertain 

 whether such differences are temporary or permanent it was 

 necessary to grow different forms simultaneously under exactly 

 the same conditions of moisture, temperature, aeration, light, 

 nutrition, etc., and further to compare their behaviour as para- 

 sites on the same hosts under the same conditions. By the kind 

 permission of Professor Barker, the writer was able to do this 

 on joining the staff of the above station. 



Work was commenced with five forms. E isolated from cotton 

 (Egypt) ; 5 and A from diseased potato in England (H. S. Stirrup 

 and Mrs N. L. Alcock) ; / from India (F. J. T. Shaw) and B from 

 the Missouri Botanic Garden, U.S.A. Later PO and W from 

 Potato and PE from Garden Pea, England (W. Buddin) was 

 added. 



