174 



preferred by them ere clso or.pable of reacting In the same wav. 

 must reijain unanswered. Me will be fully informed as to aany" 

 Of the questions referred to here only v hen it is possible to 

 produce galls artificially on various plants and parts of 

 plants under varying external conditions. Then we will >e 

 able to test experimentally ell parts of plants as to their 

 oapaoity for the formation of galls as we are now able to do 

 in the formation of oallus. 



Looking back at the speculations of the nature-phil- 

 osophers (Redl), we find that the assumption of an ex- 

 pecial poisonous action has always played the chief role 

 in the attempt at explaining the g enesis of the galls. 

 MalpighT-^ assumed that "the insect prbclucing "tlie galFex- 

 cretes a poison which causes a fermentatidn of the content 

 of the Infected plant; this fermentation exciting the ab- 

 normal growth which leads to the formation of galls, 

 Reaumur^,. to whom the secretion furnished by the gall In- 

 jects seemed too scanty to cause such extensive new forma- 

 tions, thought that a kind of suction was produced by the 

 gall-producers and inhabitants, which caused the juices 

 of the plants to flow toward the place infected. Accord- 

 ing *o nim. a rise in temperature takes place at the place 

 of stimulation, wnion tavors tissue growth, and the theory 

 stated by Malplghi has been proved capable of further de- 

 velopment; lajBaza-Duthiera^ returned In every detail to 

 Malpighi*s theory and explained galls as the products of 

 the action. of different kinds of poisons, Darwin and 

 Hofmeister later expressed the same opinion about the 

 formation of galls. If the traumatic stimuli, which Un- 

 doubtedly participate/ in the formations of many galls, 

 were overlooked or given too little Importance by the 

 authors named it maybe explained directly by the fact 

 that their attention was directed first of all to the com- 

 plicatedly constructed prosoplasmas. We will be obliged 

 to return often to the similarity of many simply construc- 

 ted galls (kataplasmas) to wo^nd tissue; which favors the 

 theory that traumatic stimuli participate in the forma- 

 tion of galls. 



(194) All previous attempts to produce " artificial" ^11 s 



by inoculation with different poisonous substances nave 

 failedi Compare, besides Bacerinck (see above), reports 

 by Knyj Kustenmacher, Laboulbena, etc. 



■'• Anatorae Plantarum, London 1676-79. 



Reaumur, M^m; pj servir. k l^hist, d. insects. T. Ill, 

 mem. IX u. X, 



2 



3 



Lacaza-Duthiers, Rech. pour servir a I'histoire des 

 gajles, Ann. So, Wat. Bot., 1853, 3°*® ser., T, XIX. p. 273, 



^ Darwin, On the origin of species, 5th edit., 1869, p. 

 572, Hofmeister, Allgem. Morph. d, Gew. , 1868, p. 634. 



Kny, Ueb, kunstl, Verdoppelung des Leitburidekreises im 

 Stamm. d.„Dikotyl. Sitzungsber. Ges. naturg. Fr/, Berlin, 1877, 

 p. 189. Kustenmacher, Beltr, z, Kenntn. d, Gallenbildungen etd, 

 Pringsheim's Jahrb, f. wiss. Bot., 1895, Bd, XXVI, p. 82, 

 Laboulbene, Essal d'luae theorie sur la production d, div. galles 

 veget. C. R. Ao§d, Sc. Paris, 1892, T. OXlV, p. 720. 



