50 BACTERIAL DISEASES OF PLANTS 



by O'Gara's disease (Fig. 355), and on wheat attacked by 

 Hutchinson's disease (Fig. 35Z)). 



Organs may be developed in excessive number or out of 

 place, as roots or leafy shoots in crown gall, witch-brooms on 

 Pinus, and incipient roots on the stems of tomato, tobacco, 

 chrysanthemum, nasturtium, etc. Hunger found a bud on a 

 tomato leaflet which he attributed to the stimulus of Bac- 

 terium solanacearum but this may have been natural (see Fig. 

 36) and an old paper by Duchartre^ who first discovered adventi- 

 tious buds on the leaves of the tomato. 



Fig. 36. — Cross-section of middle part of a tomato leaf in the region of the 

 midrib showing leafy shoots originating from the sulcus. Variety Livingston's 

 Dwarf Aristocrat. I have rooted and grown these foliar shoots into mature 

 fruit-bearing plants. Photographed June 23, 1916. X 4. 



In various diseases the plant removes starch from the vicin- 

 ity of the bacterial focus which it endeavors to wall off by the 

 formation of a cork-barrier, and in this effort it is sometimes 

 successful, if the parasite is growing slowly (Figs. 136, 174). In 

 other cases (hyperplasias) starch is stored in the diseased parts. 



The most conspicuous response of the plant, however, is in 

 the form of pathological overgrowths — cankers, tubercles, and 

 tumors. Some of these are very striking, e.g., those on the ash, 

 olive, citrus, beet {Bad. heticolum^) , pine, oleander, and on a 

 multitude of plants attacked by crown gall. In some of these 



' Duchartre, P.: Sur des feuilles ramifercs de Tomates, Ann. d. Sci. Nat. 3 

 Ser. Bot., Tome 19, Paris, 1853, pp. 241-251, Plate 14. 



2 See "Tuberculosis of Beets" in ''Crown Gall of Plants: Its Cause and 

 Remedy." Bull. 213, U. S. Dept. Agr., Bu. PI. Ind., Washington, D. C, 1911, 

 pp. 194-195, and plate XXXI V. 



