38 PLANT PHYSIOLOGY 



absorbs 81 per cent, of the incident light, allowing only 19 per cent, to pass 

 through, and of this 81 per cent., 80-3 per cent, is used in transpiration, and only 

 0-7 per cent, in photosynthesis. Since, however, the part of the solar energy 

 employed in transpiration must, without doubt, be subject to continuous and 

 great variations (due to temperature, atmospheric moisture, &c.), it must be 

 a matter of considerable difficulty to draw any sound conclusions as to light 

 energy used up in photosynthesis from observations on the variation of the 

 amount of light passing through the leaf. 



131, 1. 4, after light, read e.g. chlorophyll (TiMiRiASEF, 1903), 



1. 12, after sensitizer read in this sense. If, however, by the term ' sen- 

 sitizer ' we attach chief emphasis to the idea of a transfer of energy of the 

 absorbed light to another substance, then one may well regard the chlorophyll 

 as a member of the class of sensitizing substances (comp. MOLISCH, 1906). 



I. 21, for 2nd ed. read I, p. 292. 



II. 24-5, for 2nd ed. i, 289 read I, p. 308. 



I. 42, after ' purification '. read He showed, further, that the C0 2 of the air 

 was not only the source of the organic substance of the plant but also of the 

 oxygen given off by it, and that the humus was of no nutritive value. He also 

 had a perfectly clear conception of the extent of respiration. Hence he must 

 be looked upon as the founder of our knowledge of nutrition ; the facts that 

 he established form the fundamental basis of all we know on the subject 

 to-day. 



II. 46-54, for He showed . . . sound basis, read His studies, however, did 

 not conduce to a marked advance in the subject (\VIESNER, 1905) ; that we 

 owe, in the first instance, to TH. DE SAUSSURE (1804), wno by his accurate 

 quantitative experiments provided that solid basis for the whole superstruc- 

 ture which it required. 



132, 1. 8, after starch read not only 



133, 11. 3-4, for of which . . . here read e.g. the materials of the cell-wall, 

 fats, and numerous organic acids. 



I. 7, for every plant . . . percentage read these bodies form indeed but 

 a small part of the dry substance, but they are never absent from it 



II. io-n,for of whose . . . conception, read and thus complete our sketch 

 of their absorption of nutriment. 



1. 13, for than carbon. For read inasmuch as 

 1. 14, delete on the contrary 



134, 11. 8-9, for reaches . . . ash read consequently must suffice for further 

 development of the seedling than the amount of ash constituents present will 

 permit. 



I. 40, delete not to say the best possible 



II. 41-3, delete [How . . . say.] 



11. 47 p. 135 ; 1. 32, for It is impossible . . . injurious effects, read After 

 BOUSSINGAULT had furnished proof that the green plant thrived well with nitric 

 acid as a nutrient, the older view that ammonia was the chief source of nitrogen 

 to the plant, advocated especially by LIEBIG (1840), was overthrown. Indeed, 

 some went further and affirmed that ammonia was far inferior to nitric acid as 

 a source of nitrogen, believing that the earlier statements as to the favourable 

 effect of ammonia were entirely due to the fact that the ammonia in the soil 

 had become altered into nitric acid through the agency of micro-organisms 

 (Lecture XIX). Apparently, however, this reactionary position as regards 

 LIEBIG'S ammonia theory far overshot the mark. More recent experiments 

 (PixscH, 1887-96 ; MAZE, 1900 ; GERLACH and VOGEL, 1905 ; SOAVE, 1906) 



