20 



PLANT PHYSIOLOGY 



grown in chalk soils amounts roughly to 45 per cent, oi the pure ash, while 

 the same species contain only 30 per cent, when grown in a sandy soil. The 

 ash contains correspondingly more chlorine when the plant is grown on a sea- 

 shore, where sodium chloride is abundant, than when grown inland : 



Percentage of chlorine in pure ash (CZAPEK, Biochemie, II. 810). 



On the seashore. 20-25 km. distant from the shore. 

 Beta vulgaris (root) 15-29 12-30 



,, (leaf) 21-39 16-61 



Potatoes (tubers) 12-62 7-96 



It would be quite erroneous, however, to assume that in general the 

 amount of a certain substance in the plant depends on that present in the 

 environment. It is well known, for instance, that iodine is present in sea- 

 water only in minute traces, but it occurs in many of the tangles in relatively 

 large proportions. Inversely, a substance abundant in the environment may 

 occur in the plant in relatively much smaller amount. This fact is illustrated 

 by WOLFF'S (1871, p. 132) analysis of the ash of Lemna trisulca as compared 

 with that of the water in which the plant grew : 



Water 



Lemna 



K 2 



5-15 

 18-29 



Minerals present in 100 parts of pure ash. 



Na 2 O CaO MgO Fe 2 O 3 P 2 O 5 So 



7-60 45-56 16-00 0-94 3-42 



4-06 21-86 6-60 9-57 n-35 



3 



10-79 

 7-91 



Si(X 



4-23 

 16-05 



Cl 

 7-99 



5-55 



Why K, Fe, P, and Si should be absorbed in relatively much greater 

 quantity than the proportion in which they are present in the water is quite 

 unknown. The absorbed substances may be deposited partly in the cell- 

 wall, but certainly they are also in part taken up by the protoplasm. We 

 have already clearly established the fact that protoplasm exhibits great vari- 

 ability in its power of permitting the passage of dissolved substances, that 

 the absorption in one case goes on simply in obedience to physical laws, until 

 similar concentrations are reached in the solutions inside and outside the cell, 

 while in other cases the absorption ceases long before this equilibrium is 

 attained (Lecture II). We concluded from this that absorption of a substance 

 continues to take place, more especially if the entering solution becomes per- 

 manently altered within the cell, as in the case of certain aniline dyes. We must 

 assume that the minerals are also often accumulated in the cell because they 

 become built up into other combinations, very probably organic in their nature. 



1. 5 after table, for this view LIEBIG (1840) supported very read this view 

 was held by C. SPRENGEL (1839), an d LIEBIG (1840) supported it very 



81, 11. 20-34, f or The following substances ... of the seed read As an in- 

 stance of the results of water culture we will select out of the older literature 

 on the subject the experiments of BIRNER and LUCANUS (1866). These authors 

 used a nutritive solution which contained per litre of water about 0-5 g. MgSo 4 , 

 1-5 g. KNO 3 , i g. H 2 KPO 4 and i g. Fe 2 (PO 4 ) 2 and obtained an increase in the dry 

 weight of oats equivalent to 138 times the weight of the seed. 



1. 48 P. 82, 1. 3, for Numberless experiments . . . primary import read 

 Numberless experiments have been carried out more recently with such nutri- 

 tive solutions ; those invented by KNOP, and by SACHS more especially, have 

 been often employed. Their composition is as follows : 



KNOP (1868, p. 606; 1884). 

 0-25 g. Magnesium sulphate 

 i-oog. Calcium nitrate 

 0-25 g. Acid potassium phosphate 

 o- 1 2 g. Potassium chloride 

 Trace of Ferric chloride 



SACHS (1882, p. 284). 



i-og. Potassium nitrate 



o-5'g. Sodium chloride 



o-5g. Calcium sulphate 



o-5g. Magnesium sulphate 



o-5g. Finely ground Calcium phosphate 



Trace of Ferric chloride 



