92 



abrnidant current of nutritive substances flow to the cells in 

 vvliich a^moderately vigorous elii-nination of v;ater vapor is 

 possible. The differences, often showii by the comparison of 

 different examples of the same species under similar external 

 conditions, might be based upon dissimilar conditions of nu- 

 trition of the objects under investigation. 



EEperimental investigations into the influence of abund- 

 ant nutrition on growth and cell-division have led as yet to 

 no positive result. At least, Haberlajidt was not able to 

 bring isolated cells to celldivision by supplying abundant 

 , nutritive substances (cane-sugar) . 



Recently Yv'inkler reported in a preliminary statement 

 (loc. cit.) that isolated cells could be stimulated to divi- 

 sion by means of poisonous substances l isolated root-parenchy- 

 ma cells of Yicia Faba grew out to two or three celled threads, 

 if O.OOE per cent. C0SO4 was added to the nutrient solution 

 (Knop ^lus 1 per cent, cane-sugar) , 



5. TYLOSES 



As tyloses are -asually designated all those spherical 

 pouches found in the lumina of the ducts and tracheids of 

 various vascular plants. They are knovm to be produced by 

 the growth into the lumen of the ducts of the adjacent par- 

 enchyma cells through the thin-v;alled parts upon v^ich they 

 touch. The parenchyma cells do not divide - with very rare 

 exceptions - so that we can consider tyloses io be hyper- 

 trophies. 



Tyloses are distinguished from other hypertrophies, 

 first of ail, by the fact that in their production only a 

 limited part of the membrane of the participating cells is 

 enlarged by surface grov;th. The position of these narrowly 

 bounded, growing membrane areas is determined by the releif 

 outline of the adjacent wall of the duct. In "this way only 

 those parts of the parenchyma, cell wall distend, which do 

 not lie xmder resistant, thickened membranous parts of the 

 ducts. Therefore,' this explains forthwith the fact that the 

 formr-pro portions of the cells producing tyloses are percep- 

 tibly changed during the growth, so that the hypertrophied 

 cell is not an enlarged reproduction of the normal one. The 

 cylindrical or spherical parenchyma cells acquire one or 

 more spherical or sac-like elongated outgrowths, often of 

 considerable size, Not infrequently the volume of the orig- 

 inal cells remains far below that of this nev/ly produced 

 appendage. {Compare fig. SI). The tyloses are further charac- 

 terized by the fact that they fill out hoMrow places already 

 existing in the plant body. Thus, by the hypertrophy of cer- 

 tain cells, in the case of tyloses formation, there is brought 

 about neither increase in volume, nor change in the form of 

 the organs concerned, nor does it cause the formation of pus- 

 tules or swellings. 



All larger cavities found in the plant body,- the 

 lumina of the ducts, the air chambers of the stomata and the 

 secretion cavities, may indeed be filled up by hypertrophic 

 (99) growth of the living, adjacent cells. YiJe will summarize as 



tylose-formation all hypertrophies characterized by localized 

 surface growth of the membranes filling out any cavities in 



