IIG 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



is said to spread rapidly in the store, causing the decay of the leaf stalks 

 and rendering the crop useless.''' 



The symptoms which have been commonly associated with the 

 disease in this country very closely resemble those noticed and 

 described by Briosi and Cavara.f 



" Le fogiie del sedano vengono gravemente danneggiate da questo 

 parassito. Vi si manifestano delle macchie irregolari, dapprima 

 gialliccie poi grigie, spesso confluenti, sulle quali appajono in gran 

 numero peritec! puntiformi, bruni. Tutta la foglia in seguito passa dal 

 color verde al giallo, diventa flaccida e marcisce." 



The little black dots are the fruits (pycnidia or perithecia) of the 

 fungus, the mycelium of which invades the tissues and produces the 

 disease. Where the mycelium penetrates the cells of the leaf are killed, 

 and thus the fungus not only robs the plant of food but reduces the 

 effective area of the foliage, and so, even when the attack is not suffi- 

 ciently severe to cause decay, interferes with and reduces the amount 

 of growth made. 



The Fungus implicated. — The fungus causing the disease belongs 

 to the genus Septoria, and appears to be morphologically indistinguish- 

 able from one which causes a similar disease on parsley. | We there- 

 fore prefer to call it Septoria petroselini var, apii, the name under which 

 it was first described, instead of adopting the name Septoria apii 

 Eostrop,§ as Chester, |] Klebahn.H and some other writers have done, 

 mostly on the ground that a different host plant is involved. The 

 fungus produces pale spots, which are frequently confluent, of 

 roundish or irregular shape, on both burfaces of the leaf; in severe 

 attacks the whole leaf becomes rapidly olive-green; the perithecia are 

 numerous, sunken in the tissue of the pale spots or occurring over the 

 whole leaf, leaf stalk, stem and fruits, minute, black or almost black, 

 flattened-globose, about 180 -250 jot diam. , with a thin parenchymatous 

 coat, bursting slightly through the epidermis and opening at maturity 

 at the apex by a minute round pore, through which the spores are ex- 

 traded in a long curving, somewhat sticky mass, looking much like a 

 tendril. Spores very numerous, colourless, filiform, straight or 

 slightly curved, guttulate and septaie. The septa are often difficult to 

 see and the spores have been described by some observers as without 

 septa,'''''' but proper illumination and careful focussing rarely fail to 

 render them visible. They measure 38p-4:'2fx x l-5/^-2/i. (Fig. 62.) 



* Duggar, B. M. "Two destructive Celery Blights." U.S.A. Exjj. Stn., 

 Cornell, Bull. 132, March 1897. 



t Briosi and Cavara, I Funghi parassiti delle Pianfe Coltivate od utili, 

 1890. 



X See e.g. Saccardo, Sylloge xiv. p. 972. " *S'. Petroselini var. apii . . . . 

 maculis latis albicantibus, areolas flavidas continentibus ; peritheciis sporuligque 

 ut in typo." Briosi and Cavara point out slight differences m size from the 

 typical, form, but the range of variation in that is very wide, and the differences 

 pointed out do not appear to carry this beyond that range. 



§ Rostrup, Gordners Tidende, 1893, p. 180. 



II Chester, Bvll. Torr. Bat. Club, 1891. p. 372. 



H Klebahn, H., " Krankheiten des Selleries." Zcif.^. fiir Pftanzcnhr. (1910). 

 p 4 et seq. and Mitteil. Deutsche Landic. GeselL, pp. 63-67. 



** E.g. Sorauer, "Die Fleckenkrankheit des Selleries," Zeifs. fii?' Pfianzenhr. 

 vi. (1896) p. 191. 



