48 PLANT PHYSIOLOGY 



the ash taken up by a large number of cultivated plants must pass back again 

 into the soil. 



From the experiments of PURIEWITSCH, referred to in the last lecture, 

 it is known that the permeability of the protoplasm in self-emptying stores 

 of reserve is inconstant, and WACHTER has more recently investigated this 

 point more in detail in the case of the onion. He finds that the emptying, the 

 exudation of glucose and non-reducing sugar, is, as a rule, always incomplete, 

 ceasing when the concentration within the cells has reached a certain value. 

 That the concentration outside is of no importance is shown by experiments 

 with varying amounts of water, and also with salt solutions ; certainly there 

 was, as in PURIEWITSCH'S experiments, a retardation of the outflow in the 

 presence of such salt solutions, but the amount showed no ratio to the con- 

 centration of the salt. In addition to salts, PURIEWITSCH says that chloro- 

 form and oxygen have an effect on the outflow, and CZAPEK has (1897) also 

 shown that emptying is inhibited by chloroform in the case of the petiole. 

 While granting the possibility of the alteration of the quality of the plasmatic 

 layer by anaesthetics we must 



11. 39-40, for is quite as great in the latter as in water read is certainly 

 not as great in the latter as in water (NELL, 1905). 



169, last line P. 170, 1. 15, for It must not . . . minute canals read Whether 

 the cell-wall or the plasmatic layer presents the greater difficulties in the 

 way of diffusion we do not know. The pits, however, which are never absent 

 from a cell-wall, are at least adapted to further a transport of materials from 

 cell to cell, and that in two ways : first, inasmuch as the membrane, where 

 they occur, is generally much reduced in thickness, and secondly, because of 

 the fine pores existent in the pit-closing membrane. Since adjacent proto- 

 plasts are by means of these canals placed in communication with each other, 

 it might be supposed that fragments of the protoplasm or even starch grains 

 might pass over by this means from cell to cell ; 



11. 32-4, for According to ... short ones read In spite of the pits every 

 transverse wall would appear, all the same, to offer a certain amount of opposi- 

 tion to the transport of materials, and hence we see this transport taking 

 place more readily in long cells, in which there are only few transverse parti- 

 tions to be passed through, than in short cells. 



171, 11. 3-5, for Although CZAPEK ... is the case, read CZAPEK brings forward 

 the following experiment in support of his view. 



1.14, fl/^necessary^fl^(comp.HABERLANDT,PAys.ylw^.;CHAVEAUD, 1897). 



I. 27, delete [HABERLANDT . . . view.] 



II. 30-4, for The sugar . . . carbohydrates, read The sugar arising from 

 the transformation of starch, after migrating through the assimilatory cells 

 and the bun die -sheath, eventually reaches the sieve-tubes, more than half of 

 whose dry weight often consists of sugar (KRAUS, 1885). 



1. 32, for 592 read 580. 



1. 40, after 363) ; read it is by no means easy to decide whether proto- 

 plasmic movement takes place in the sieve-tubes of the uninjured plant or not, 

 for observations on isolated portions prove little ; 



172, 11. 19-22, for It is more . . . evidence, read It is improbable that sieve 

 tubes are aided in the performance of their functions by lacticiferous tubes 

 (KNIEP, 1905). 



1. 25, for from a few to more than read several to as many as 

 1. 36, for effected read effective 



173, 11. 22-4, for A transference . . . taking place read Under certain con- 

 ditions, however, storage of reserves may take place 



