﻿224 BOTANICAL GAZETTE [march 



end of the cell and therefore nearer the plane of final separation, 

 in the event that this supervenes (text fig. i, a, b). 



(2) The cell grows longitudinally, the maximum extension of 

 the walls occurring where the maximum softening has taken place, 

 and concurrently with it. The length of the cell may increase 

 four or fivefold. The total length of the longest cells in the pros- 

 enchyma sheath at the time of separation has been found to be 

 0.2 mm. or slightly more (text fig. 1, c, d). 



The protoplasmic utricle also becomes greatly extenuated 

 during this period of growth and the cytoplasmic membrane is 

 most delicate. The nucleus is disposed in the transverse zone of 

 elongation, usually increases in size, and remains perfectly normal 

 in appearance until the completion of separation and even still 

 later (text fig. i,h). It may lie against the wall or be suspended in 

 or near the axis of the cell. Occasionally a very delicate trans- 

 verse wall is laid down just previous to or at the time of elongation. 

 Transverse walls may have been formed still earlier, but the fact 

 that the cellular activity may take this form during the process 

 leading to separation must be taken as evidence of vigor rather 

 than of degeneration. Further, it is not possible to suppose that 

 this behavior is consonant with a loss of turgor, supposed by 

 Hannig to occur, while the disappearance of the starch suggests a 

 constant accession of solutes for maintaining turgor. 



It is of prime importance, in view of the purpose of this paper, 

 to analyze fully the changes undergone by the walls which display 

 elongation. These are more readily appreciable in the thickest 

 of them. The wall shows first of all evidence of chemical alter- 

 ation resulting in a physical change which allows it to be drawn 

 out." There is no evidence that the middle lamella alone is 

 altered, but rather does it appear that the whole wall, excepting 

 only a delicate membrane limiting the lumen of the cell, is softened, 



is affected by enzymes, see Jones, L. R., Pectinase, etc. N.Y. Agric. Exp. Sta. 

 Tcchn. Hull. 11. Nov. iqoq. 



