cxliv PROCEEDINGS OF THE ROYAL HORTICULTURAL SOCIETY. 



Harpalmm (Miss Mellish) x Helianthus multiflonts, they entirely agreed 

 with it, as also with a hybrid bet^veen Harpalium and H. multiflorus 

 from a friend. If, therefore, Mr. Buffham's be a cross between the 

 annual and perennial varieties, then the latter is so strongly prepotent or 

 dominant " that no trace of its parentage is present. 



Cuciimber-leaf Disease. — Some leaves having been sent for examina- 

 tion, Dr. Cooke reported : — " They are evidently badly infected with the 

 same mould as that we described in 1896 on the leaves of Melons from 

 Totteridge under the name of Cercospora melonis. The leaves become 

 spotted with rounded spots up to half an inch in diameter, such spots 

 being of a pale ochry colour, brittle, and soon cracked and broken. It is 

 difficult with a lens to detect any mould on these spots, but when 

 submitted to the microscope the entire substance is found to be traversed 

 by mycelium, which sends up long, slender, olive-tinted hyphfe, which 

 reach upwards of 150 micromillimetres in length. These hyphie bear 

 long characteristic conidia which attain from 80 to 140 micromillimetres 

 in length and about 7 or 8 in thickness — much thicker than in the 

 majority of species in this genus. They are slightly attenuated upwards, 

 and rounded at both extremities, at first with a row of guttules, and 

 ultimately multiseptate. The conidia are hyaline, with scarcely any 

 tinge of colour, generally slightly curved. 



" There is no doubt but that this is the same species as that which 

 attacks the leaves of Melons. 



" The great practical question which at once suggests itself is, ' What 

 is the remedy ? ' In this instance we have to deal with an endophytic 

 fungus, the mycelium of which permeates the tissues, and has obtained a 

 firm footing before any spots appear on the leaves or the plants give any 

 other indication of the presence of the pest. The mischief is all done 

 when the leaves are spotted, and then it is useless to spray with an 

 ammoniacal carbonate-of-copper solution, as has been recommended in 

 similar cases, because the spraying is only superficial, and has no eflt'ect 

 whatever upon the mycelium within the tissues, w^hich will still continue 

 to flourish. The only hope lies in the prevention of the spread of the 

 disease to other and healthy plants. The cultivator must be the judge 

 whether it is better to sacrifice and destroy the infested plants at once, 

 since he cannot hope to save them after the disease has broken out. As 

 we are uncertain whether the full description of this parasite has ever 

 been published otherwise than as a note in the Gardeners' Clironicle, 

 September 5, 1896, we repeat it here : — 



" ' Gercospora melonis, Cooke. Spots bleached, ochraceous ; rounded, 

 about 1 cm. broad, soon breaking up. Hyphae slender, elongated, 

 olivaceous, simple, septate, 150 fj. long. Conidia cylindrical, slightly 

 curved, rounded and obtuse at the ends, attenuated upw^ards, multi- 

 nucleate, at length 5-7 septate, hyaline 80-140 x 7-8 On leaves of 

 Melons and Cucumbers.' " 



