288 Hakris M. Benedict 



of fatty degeneration are found in senility in cartilage and in other body 

 cells, indicating loss of power of assimilation or inefficient katabolism. 



Accumulation of pigment in the cytoplasm. — Hodge (1895) found a dif- 

 ference in accumulation of pigment in the cytoplasm between young and 

 old cells of the spinal ganglion of man. It has been stated that pig- 

 ments are excretory masses and that they increase with age. 



Deterioration of nucleolus. — The nucleolus diminishes in mass and in 

 staining power. It was Hodge also who first pointed out this fact. Hert- 

 wig (1904) emphasized the relation between size of nucleolus and cell 

 activity. 



INVESTIGATIONS ON SENILITY IN PLANTS: GENERAL 



REVIEW OF LITERATURE 



A review of the changes that have been discovered in perennial plants 

 as a result of senility shows that no investigations comparable to the ones 

 above cited have been made. Such statements as are commonly found 

 regarding the effect of age are based on casual observations rather than on 

 investigations. The reason for this seems to be the tacitly accepted belief 

 that, since new leaves and twigs and roots are constantly being formed from 

 persisting embryonic cells, senility as present in animals is out of the 

 question, and the term as used for plants means merely that conditions 

 have become so unfavorable that the growing parts are killed. 



This view has been further encouraged by the very great age attained 

 by certain trees, as, for example, the sequoias, the cypresses of Mexico, 

 and the baobab of Cape Verde — the last named estimated by Adanson 

 to be over five thousand years old. Therefore, the idea that trees have the 

 potential power to live forever if the conditions due to their increasing 

 size — injury from winds, greater distance from the soil, and other harm- 

 ful effects — could be prevented, is not so much formally accepted as 

 passively assumed. 



Such statements as have been published are almost entirely from the 

 pens of fruit growers. Among the first of which the writer has found 

 record are the papers by Thomas Andrew Knight, the justly famous 

 English horticulturist, to which reference will be made later. Zorn (1890), 

 nearly one hundred years later, gives about the same list of effects of age, 

 and his list in its conclusion does not fall far short of present knowledge. 

 He says that in old age fruit trees bear less, are later in maturing their 



