NOTES AND MEMORANDA. 167 



conidia), Hymenomycetes (basidiospores and conidia), and Gastero- 

 mycetes (basidiospores, and gemmfe or portions of the mycelium). 

 While the Fungi attain their highest development in the Ascomycetes, 

 the Algfe pass on, through Characese, to the Muscinete. 



Fungoid Diseases of Plants. — Disease of Chestnut Trees. — 

 M. J. De Seynes (in continuation of a paper by M. J. E. Planchon, 

 previously published *) describes a disease which attacks the roots of 

 chestnut trees.f The parasitic mycelium, which is analogous to that 

 of certain Dematiei or Zasmidium cellare, forms a su^jerficial network, 

 and also one which penetrates the tissues and destroys the cellular 

 layers which are the richest in protoi)lasm, the fibres of the liber and 

 the woody fibres not being attacked. One of the symptoms of the 

 action of the parasite is that the growth of the young radicles longi- 

 tudinally is arrested, but the diameter increases, so that they 

 ultimately form olive-like bodies, attached to the parent branch by 

 jiedicles. 



In a subsequent paper,| M. Planchon, referring to the doubts he 

 had expressed as to the species of fungus which the mycelium which 

 attacks the trees gives rise to, states the reasons which " lead him to 

 suppose to-day that the agaric in perspective is almost certainly 

 Agaricus melleus of Vahl." 



Fungus^ Disease in Lettuces (Peronospora gangliiformis, Berk.). — 

 Lettuces have been invaded for some years, in France, by a disease 

 which impedes the development of the plants, and spots and dries 

 up the leaves. The havoc has been so considerable that a small 

 body of market gardeners have ofi'ered a prize of 10,000 francs to 

 whoever will put a stop to it. 



M. Max Cornu has found § that the disease is produced by a 

 parasitic fungus {Peronospora gangliiformis, Berk.), which frequently 

 attacks other plants, groundsel, and especially the artichoke, where 

 the disease is hidden by the down of the leaves. It gives rise on the 

 inferior side of the leaves to whitish mealy tufts, whence the popular 

 name of " meunier " (miller). 



In tearing off a strip of the epidermis of a lettuce attacked, we 

 observe conidiophorous filaments, issuing through the opening of the 

 stomata, as in other species of the fungus. They are in groups of 

 two or three, or single ; their superior jmrt is variously ramified ; the 

 whole presents the appearance of a little tree. The little branches 

 are dilated at their extremity, and bear from three to six sterigmata, 

 which give rise to the conidia. These are broadly oval, with an incom- 

 plete papilla ; the germination gives rise to a filament sometimes 

 torulose in a remarkable manner. 



The gardeners attribute the malady to the west winds, and to rainy 

 and mild weather ; it may be understood by this that these conditions 

 favour the dissemination and germination of the spores on the young 

 plants, for it cannot be a question of spontaneous generation. 



* ' Comptes Eendns,' vol. Ixxxvii. (1878) p. 583. 



t Ibid., vol. Ixxxviii. (1879) p. .36. 



X Ibid., p. 65. 



§ Ibid., vol. Ixxxvii. (1878) p. 801. 



