206 Miss Dale, On certain outgrowths {Intumescences) 



Tomaschek 1 describes on Ampelopsis hederacea, generally on 

 the young twigs, the tendrils, the leaf-stalks and on the back of 

 the leaf veins, but especially on the stipules, certain "pearl-" or 

 " drop-like" outgrowths which were not due to parasitic plants or 

 animals, but to external conditions. Of these conditions Tomaschek 

 regards light as the most important, because the outgrowths 

 occurred most abundantly on some etiolated twigs which had 

 grown into a half-dark garret, and because on the normal parts of 

 the plant there were only a few on the sunny side of the stem. 



The outgrowths arise in the young parts of the axis which 

 are still in the bud. They only occur below a stoma, and there is, 

 at the apex of each outgrowth, a scarcely modified stoma. The 

 outgrowth begins in the subepidermal parenchymatous cells 

 below the stoma. These elongate and block the respiratory 

 cavity. Later they increase in number and lift up the epidermis 

 and guard-cells to form an outgrowth which becomes constricted 

 at the base until it is nearly spherical. Later, in the autumn, 

 Tomaschek found the place of these outgrowths occupied by 

 lenticels. 



This author considers that the outgrowths may, by blocking 

 up the stomata, reduce the quantity of oxygen entering the plant, 

 so that, in consequence, the formation of organic acids is 

 diminished, and the decomposition of the chlorophyll in the dark 

 is retarded. 



The appearances described by Tomaschek resemble in many 

 points those on Hibiscus, the main point of difference being 

 that the outgrowth not only begins in, but is practically confined 

 to the chlorophyll-bearing cells below the stoma, while the epider- 

 mis (as far as can be judged without figures) is merely lifted up, 

 whereas in Hibiscus vitifolius the latter is the tissue chiefly 

 concerned. 



Also, Tomaschek does not mention the occurrence of the out- 

 growths on the laminas of the leaves, and in Hibiscus they are 

 abundant there. As in Hibiscus, so in Ampelopsis, the outgrowths 

 ultimately dry up. 



Masters 2 mentions, but does not describe, some " warts " which 

 appear on the leaves of potatoes, when grown in too close and 

 moist an atmosphere. They resemble those which occur on vine- 

 leaves. 



Frank 3 and Sorauer 4 have described in various plants out- 



1 Tomaschek, "Ueber pathogene Emergenzen auf Ampelopsis hederacea," 

 Oester. Bot. Zeitschrift, 1879, p. 87. 



2 Gardener's Chronicle, 1875, p. 802. 



3 Frank, Krankheiten der Pflanzen, Bd. in., 1896, p. 313. 



4 Sorauer, Handbuch der Pflanzenkrankheiten, Zweite Auflage, Bd. I., 1886, 

 pp. 222—227, 233—237. "Die Lohkrankheit an Kirschen," Bot. Zeitung, 1889, 

 p. 182. 



