ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 419 



from the basidial form of Mycena, through Galera and PsatJiyra, to 

 Coprinus. The third group, with long basidia, can also, with the 

 exception of Lactarius and Bussula, be arranged in a series of relation- 

 ship, the highest forms of which are Amanita and Volvaria. 



With reference to the formation of sterigmata and the abstriction 

 of spores, Heese dissents from the view that the same basidium may 

 produce spores several times. He adduces several instances of dual 

 sterigmata. 



The cystidia may be used for the distinction of species to a much 

 greater extent than the basidia, in relation to their position, size, and 

 form. They may be fusiform, pear-shaped, and pointed at the end, 

 capitulate, or hair-like. The writer is unable to determine their 

 function. 



The colour of the spores is characteristic ; they should be observed 

 both dry and moist, as they frequently change their form when 

 moistened. The size of the spores has no relation to the size of the 

 fungus, but only to that of the basidia. In the white-spored sub- 

 genera, the spores have a tendency to be rounded and shorter ; light 

 brown spores are mostly ovoid, dark brown spores ellipsoidal ; black 

 spores are always ellipsoidal. 



Formation of Gum in Trees.* — Sir James Paget draws attention to 

 some remarkable investigations made by Dr. W. Beyerinck | in con- 

 nection with the formation of gum in trees. Dr. Beyerinck found that 

 in the peach, apricot, plum, cherry, or other trees bearing stone-fruits, 

 the formation of gum may be caused by inserting a portion of the 

 gum under the edge of a wound through the bark. The observation 

 that heated or long-boiled pieces of gum would not produce this effect, 

 and that wounds made in the bark of the tree did not produce gum 

 unless a portion was first introduced into it, led him to suspect that 

 the formation of gum was due to the presence of bacteria or other 

 living organisms. On microscopical investigation he found that only 

 those pieces of gum containing spores of a highly organized fungus, 

 belonging to the Ascomycetes, had the power of conveying the gum- 

 disease or gummosis, and that these spores, inserted by themselves 

 under the bark, produced the same pathological changes as did the 

 pieces of gum. The fungus has been examined by Professor 

 Oudermans, who has ascertained it to be a new species, and has 

 named it Coryneum BeyerincJcii. Its chief characters consist in 

 the fact that it has a cushion-like stroma, composed of a bright 

 brown parenchyma, on which stand numerous conidia having 

 colourless, unicellular and very slender stems, about as long as 

 themselves. The conidia are small, cask-shaped, about one-third 

 of a millimetre in length, and usually divided by slightly con- 

 stricting septa into four cells, of which the two terminal are longer 

 than the two middle ones. From these cells germinal filaments may 

 proceed, from which are developed brown, thick- walled, and many- 

 celled mycelia. The first symptom of the gum-disease is the develop- 



* Bull. Torrey Bot. Club, xi. (1884) pp. 33-4 from ' Medical Times.' 

 t Arch. Neerl. Sci. Exact, et Nat., xix. (1884) pp. 43-102 (2 pis.). 



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