592 



TRANSLOCATION 



especial importance in translocation by transferring the plastic materials 

 from cell to cell mainly in the form of non-diosmosing substances. 



The above account of the phenomena of translocation is based mainly upon 

 the researches of Pfeffer (Landw. Jahrb., 1876, Bd. v, p. in). It is at present 

 impossible to distinguish clearly between the actual translocatory substances and 

 those which undergo transitory storage along the conducting channels, for it is still 

 doubtful whether sugar, asparagin, &c. are stored up in the form of non-diosmosing 

 compounds, or whether it is the protoplasmic activity which determines their reten- 

 tion within the cell or their transference in either direction. It is, however, certain 

 that glucose, cane-sugar, asparagin, and certain proteids are able to penetrate the 

 cell-walls and living protoplasts, and hence may be directly absorbed or excreted as 

 such, while living cells may also absorb finely emulsified fatty oils. All such 

 substances are therefore capable of diosmotic transference, but it does not follow 

 that they function as translocatory compounds in all plants, for in addition to the 

 existence of specific peculiarities, different plants frequently utilize the same 

 materials in a variety of ways. Thus in certain plants the stored fatty oils are 

 partially translocated in the form of glucose, but in other cases, where the conducting 

 channels become filled with oil, the latter may undergo direct translocation (seed- 

 lings of Linum usitatissimum, Cannabis sativa, Papaver somniferum, Altium cepa '). 

 Cane-sugar is also capable of diosmotic transference, but in the beetroot it is not 

 carried in this form to the growing stems and leaves. Similarly proteids may be 

 directly translocated, although usually they undergo previous decomposition into 

 amides, &c., which in Pangium edule is accompanied by a formation of hydrocyanic 

 acid. It is quite possible that substances capable of direct translocation may 

 accumulate in the storage receptacles, or even in the cells of the conductory 

 channels, side by side with others, such as starch, in which a preparatory modifi- 

 cation must precede translocation. Many substances, however, mainly occur in 

 the storage receptacles, whereas others are found wherever translocation is active. 



SECTION 109. Special Examples of Translocation. 



Only a few of the commoner instances of storage and translocation 

 can be mentioned, and for further details reference must be made to the 

 quoted literature. No essential difference exists between the food-sub- 

 stances which are intended for immediate consumption and those which 

 are retained during long resting periods, for the latter may be artificially 

 shortened or suppressed, while substances which normally are only transitorily 

 accumulated may remain intact for long periods of time when vital activity 

 is depressed to a minimum. Seedlings and isolated parts, which are able 

 to nourish themselves only after a certain stage of development is reached, 



1 Sachs, Bot. Zeitung, 1863, p. 57; Jahrb. f. wiss. Bot, 1863, Bd. Ill, pp. 213, 251; R H. 

 Schmidt, Flora, 1891, p. 342 ; Leclerc du Sablon, Rev. gen. d. Bot, 1895, T. vn, p. 149. 



