﻿LLO I D — A BSCISSION 



walls remain deeply stained. The relation is the same to ruthe- 

 nium red, but not so markedly. 9 One must distinguish between 

 the staining capacity of the entire wall of the abscission cell before 

 elongation sets in, and that of the delicate membranes which con- 

 tinue to invest the protoplast during and at the culmination of 

 elongation. The latter seem to stain readily, at least more so than 

 the former. 



(4) The optical quality of the walls is clearly altered, since, 

 with the iris diaphragm at a given opening, a much more narrowly 

 outlined object picture is obtained than in the case of an unaltered 

 cell. Hannig states that this condition obtains (pp. 428-429). 



(5) There is a readily appreciable amount of swelling of the 

 cell walls, most marked in those which are thicker. Consequently, 

 the thick-walled cells of the collenchyma and prosenchyma sheath 

 are most favorable for observation. This phase appears to be 

 passed through quite quickly. Transverse sections display this 

 condition most abundantly (text figs. 1, a, b; 2, a, b, c; pi. figs. 5, 

 6, i 2 , 13). 



(6) Following this the walls become altered to such an extent 

 that, when successfully stained with ruthenium red, the substance 

 of the wall appears as a flocculated mass, separated from the pro- 

 toplasm by a delicate membrane (pi. figs. 6, 13). Whether the 

 flocculation is due to the preservation in alcohol or to the action of 

 ruthenium red 1 " matters less than the fact that the walls are in 

 a condition either of flocculation or in one which allows it. When 

 in this condition the walls frequently show breaks of such character 

 that they can be explained only on the supposition that it is in 

 the condition of a gel. As abscission nears completion, this granu- 

 lar matter is much reduced in amount, apparently by hydrolysis. 

 The product may be absorbed by the abscission cells, for which it 

 may very well be regarded as a source of energy. It is not super- 

 fluous to insist that this granular matter is not cytoplasm, although 

 it may easily be mistaken for it, especially as displacements of the 



9 Successful differential staining is obtained best by means of quite dilute solutions. 

 10 1 have noticed that ruthenium red flocculates the pec tic ( ?) mucilages derived 



- rial of Mirabilis. 



