91 



become gradually smaller, assumed a yellov^ish. tinge 

 and were transformed finally into very delicately 

 contoured, small leucoplasts. When kept in a one 

 per cent, sugar solution, they decrease a little 

 in size, but keep their color; in stronger concen- 

 tration (3 to 5 per cent.) they remain as large and 

 as richly pigmented as before and often become more 

 intensely green than they were originally. Therefore 

 (97) those same changes may' appear in the culture of cells 

 in inorganic solutions, which we have found to so 

 often occur in hypertrophied cells v;ithin normal 

 tissues. Future investigations will determine, 

 whether it is possi ble to bting to hypertrophy cells 

 left in the tissue and then, by a simultaneous sup- 

 plying of carbohydrates or other nutritive substan- 

 ces, to prevent the retorgression of their chloro- 

 phyll contents, Haberlandt assumes that, in isola- 

 ted cells, the chlorophyll grains thro\'m upon their 

 own assimilation activity cannot be kept intact, 

 since they give up their assimilatory products to 

 the other cell-organs. Isolated assimilatroy cells 

 of Eichornia crassipes soon lost their cllorophyll 

 contents' in the dark, if at the beginning of the 

 experiment they contained no starch, "while they 

 remain intact if, in case of scanty or insignifi- 

 cant growth of the cells, they can make use at least 

 partially for themselves of the' starch stored up in 

 them". Haberlandt obtained also giant cells with 

 thickened walls in the culture of fragments of stsm- 

 inal hards of Trades cant ia. 

 Winkler (Bot. Zeitg. , 190E, Bd. LX, Abt. E, p. 264) 

 promised further communications concerning the fate of 

 isolated cells. 



The conditions . under which the abnormally large cells, 

 termed callus-hypertrophies, are produced, are still unknown 

 to us. Of the diverse new conditions which an injury creates 

 for the estposed cell, it has not yet been possible to separ- 

 ate the stimulating ones from the ineffective, nor to recog- 

 nize the significance of the single factors by comparative 

 experimental studies of their specific effects. More acces- 

 sible for esjierimental research is the problem, under what 

 conditions tissues of the same kind may be stimulated by in- 

 jury to hypertrophic or to hyperplastic changes. Doubtless 

 humidity plays a large part here; air containing much water 

 vapor pi-omotes extensive undivided grovrth, after injury to 

 living tissues, just as in the case of hyperhydric ones. 

 One of Massart^s experiments (loc. cit. ) supports this. He 

 so split a stem of Ricinus by lateral pressure that two^ slits 

 were opened tov/ards the -oith-cavity, two others toward the 

 outside. fCompare fig. 38). In the slits f. f. opening to- 

 wards the outside, the exposed tissues reacted with abundant 

 cell^division; in f» f « , on the contrary, only callus hyper- 

 trophies appeared. Massart assumes that contact v/ith the 

 open air makes pos^ble the extensive reaction in the first 

 named slits, A comparison with different researches makes it 

 seem certain to me that the effect of moist air, which we may- 

 presuppose to be present in the pith-cavity of the stem, was 

 198) the essential condition of MassartSs experiment. The signifi- 

 cance of transpiration lies supposedly in the fact that a more 



