HYPOCHNUS 391 



interwoven mesh of stout, much branched, septate hyphae, 

 from which spring here and there small tufts of basidia. This 

 fungus has been stated by an American mycologist to be the 

 fruiting condition of Rhizoctonia violacea (Tul.). I have met 

 with this fungus on potatoes many times, but could not trace 

 any connection with Rhizoctonia. This subject is discussed 

 in more detail under Rhizoctonia. 



When the spores of H. solani are sown on the cut surface 

 of a potato tuber, a dense uneven crust of mycelium is 

 produced, and the surface eventually becomes covered with 

 scattered tufts of basidia. There is no approach to a compact 

 hymenium, as in the genus Corticium, and all the mycelium 

 remains perfectly colourless. 



I have never noted any injury arising from the presence of 

 this fungus on potato haulms, in fact the entire film is readily 

 removed by slight rubbing, and I have not succeeded in 

 detecting haustoria in the epidermal cells of the host. 



Prillieux and Delacroix, Bull, de la 'Soc. Mycol. de France, 

 1891. 



Cucumber collar rot. This mischief is caused by Hypoch- 

 nus cucumeris (Frank), and is not uncommon in this country, 

 although I am not aware that it has been previously recorded 

 as a British fungus. It attacks the stem at the soil level, and 

 covers it with a thin greyish" film of interwoven hyphae for a 

 distance of three to four inches. The mycelium penetrates 

 the tissues and soon chokes up the vessels, etc., thus cutting 

 off the supply of food and water. When a plant is attacked 

 the leaves wilt and turn yellow, and the stem collapses within 

 a few days. 



Frank says that this fungus also attacks clover and lupins. 



The mycelium forms a very thin, inseparable stratum, loose 

 and fibrous in texture, basidia scattered, cylindric-clavate, 

 spores elliptical, 7-8 x 5 /*. 



The only practical method of guarding against this disease 

 is by destroying the mycelium or spores present in the soil ; 

 this may be done to some extent by mixing it with kainit some 

 time before it is used. Leaf mould is most likely to contain 

 the fungus. When the disease attacks the plants, it may be 

 checked to some extent by watering with a solution of 

 sulphate of potash. 



Frank, Hedwigia, 1883 ; and in Ber. d. deutsch. Bot. Gesell., 

 1883. 



