SUPPLEMENT 19 



1. 41, add (After the MS. of this lecture had been completed there appeared 

 a paper by URSPRUNG (1907) dealing in a very critical manner with the various 

 possible methods of ascent of water.) 



77, 1. 50, after matter read by LAVOISIER 



78, 1. 22 P. 79, 1. 23, delete The nature of the salts . . . constituent of plant 

 ash. 



79, 11. 24-49, f or The total amount ... by italics read The total amount 

 of ash depends, in the first instance, on the specific peculiarities of the plant, 

 for different species grown on similar soils give different percentages of ash. 

 WOLFF'S Ash Analysis (p. 137) shows us that, of several common weeds grown 

 in the same soil, the ash of Rumex Acetosella amounts to 8-14 per cent., of 

 Geranium dissectum to 9-98 per cent., of Sedum Telephium to 11-96 per cent., 

 and of Myosotis arvensis to 17-85 per cent. The existence of specific differ- 

 ences between plants in amount of ash may also be deduced from the tables 

 given in Lecture I (pp. 3, 5). These tables give averages of, often, very numerous 

 analyses, for, as may be readily imagined, the amount of ash varies extremely 

 in individual plants according to circumstances. Thus in a substratum in 

 which there is much mineral matter, either soluble or actually in solution, 

 the amount of ash rises, but vigorous transpiration, more especially, increases 

 the absorption of water and thus also increases the quantity of mineral matter 

 in the plant. According to EBERMAYER (1884) the leaves of actively transpir- 

 ing trees, such as the ash or willow, contain 7-10 per cent, of ash, while those 

 of the feebly-transpiring pine contain only about 1-5 per cent. It is readily 

 comprehensible that the leaves are the organs richest in ash, since the greatest 

 evaporation takes place there, and since it is in them that the minerals accumu- 

 late, carried there by the transpiration current. Stems are always for this 

 reason poorer in ash, as the following table shows : 



Percentage of minerals in dry weight (CzAPEK, Biochemie, II. 781) 



Lupinus luteus Nicotiana Tabacum Brassica Rapa Achyranthus aspera 



Leaves 6-06 11-87 20-84 2 4-33 



Stems 3-86 7-73 9-18 8-67 



In certain leaves the amount of ash is even greater, e.g. 30 per cent, in 

 Beta vulgaris and 50 per cent, in Mesembryanthemum crystallinum. Since, as 

 we shall presently find, the ash is not superfluous, much less injurious, but on 

 the contrary is a quite essential constituent of the plant, transpiration must 

 be an exceedingly important process, and must not be regarded in the light 

 of a necessary evil (comp. p. 43). 



The individual elements which occur regularly in appreciable quantity 

 in the ash of all plants are only nine in number, i. e. Cl, S, P, Si, and the metals 

 K, Na, Ca, Mg, Fe. The following table (WoLFF, 1880) shows the composition 

 of the ash of certain plants ; the special abundance of an element is emphasized 

 by italics : 



80, after the table read 



In addition to these nine elements which have been determined quanti- 

 tatively, aluminium and manganese are also as a rule demonstrable, and it is 

 further possible to determine here and there the presence of traces of a large 

 number of other elements whose names we need not mention. 



Confining ourselves to substances which have been quantitatively deter- 

 mined, we may next ask more exactly whether any relations exist between 

 the amount of these bodies present in the soil and the amount present in the 

 plant. Such relations can actually be demonstrated. MALAGUTI and DURO- 

 CHER'S (1858) analyses show, for example, that the calcium carbonate in plants 



B 2 



