254 MISS MARIETTA PALLIS ON THE 
Evidence that the death of the reed follows on senescence presumes proof, 
(1) that the different-sized shoots do not belong to different varieties of reed 
(see pp. 263 & 264), and (2) that death does not result from external 
agencies such as (а) unsuitable chemical or physical factors in the environ- 
ment (see рр. 264-266), ог (5) inter-competition with other plants (see 
рр. 266 & 267). 
Consideration of these questions led me to theoretical conceptions out 
of which arose the attempt to define the reed individual and finally the 
question: what is the volume and mass of the major plant unit of which 
the single reed-shoots, the minor individuals, are the parts ? 
As regards the major unit I shall offer further on (see pp. 268 & 269) a 
suggestion with the full realization that it is nothing more. Nevertheless 
I believe that it rests on an actuality. 
As is well known, the general biological questions here involved,—for 
example, the question of the adequacy of “ vegetative reproduction" as 
regards the continuance of life in a species,—have been under discussion 
for a long time, in particular, recently, through the medium of the Protozoa * 
—] refer to the hotly debated question of the Life-Cycle—though plants 
have had their place in the discussions. 
The late Professor Minchin f, referring to the Life-Cycle of the Protozoa, 
says :—“ The cultivated banana-tree is propagated entirely by a non-sexual 
method—namely, by the preduction of suckers growing up from the roots, 
and in no other way. Whether this complete abolition of sexuality will in 
time lead to exhaustion of the cultivated race of banana remains to be seen, 
but at present there seems to be no sign of loss of vigour under culti- 
vation.” 
The first important publication touching on senile decay in plants was 
the work of Thomas Andrew Knight ; it appeared in 1795 f. Since his day 
there have been several publications of varying interest on the question, 
the most recent of which is that of Professor Benedict of Cincinnati §, 
* A series of papers on the Life-Cycle of the Protozoa have appeared since the time of 
Ehrenberg, 1831 onwards to date. (See the papers on this subject by Calkins & Woodruff. 
In particular :— Woodruff, L. L., & Rhoda Erdmann, “ A Normal Periodic Reorganization 
Process without Cell-fusion in Paramecium,” Jour. of Exp. Zool. Nov. 1914; and Calkins, 
С. N., “Cycles and Rhythms and the Problem of ‘Immortality’ in Paramecium,” The 
American Naturalist, Feb. 1915.) 
t Minchin, E. A., “An Introduction to the Study of the Protozoa.” London, 1912. 
(See p. 136.) 
I Knight, T. A., “Observations on the Grafting of Trees," Phil. Trans. Royal Soc. 
London, 1795 : 2 : 290-295, fide Benedict; and * On the parts of Trees primarily impaired 
by Age," Phil. Trans. Royal Soc. London, 1810: 178-183, fide Benedict. 
$ Benedict, H. M., “Senility in Meristematic Tissue," Science, March 15, 1912; and 
“Senile changes in the Leaves of Vitis vudpina, L., and certain other Plants," Cornell 
University Agricultural Experiment Station of the College of Agriculture, Memoir no. 7, 
June 1915. 
