SUPPLEMENT 31 



by SACHS for the same plant. Other plants, however, exhibit far greater 

 assimilatory activity, while in those enumerated in the second series assimila- 

 tion is much lower than in Helianthus. These four plants, however, possess 

 sacchariferous leaves (see p. in), for under ordinary circumstances they form 

 no starch ; it would appear that assimilation is, in general, more active in 

 amyliferous than in sacchariferous leaves. 



The mention of amyliferous and sacchariferous leaves leads us to follow 

 out quantitatively also the carbohydrates appearing during assimilation, 

 which we have previously spoken of from the qualitative point of view. 

 Hitherto we have always spoken of the increase in dry weight or in carbo- 

 hydrate. In SACHS'S memoir, on the other hand, it is always ' starch-forma- 

 tion ' that is spoken of, for at that time all products of assimilation were 

 assumed to be deposited in that form. 



1. 44, after experiments read with the half-leaf method. 



1. 50 P. 115, 1. i, for MEYER'S studies ... in detail, read BROWN and 

 MORRIS'S studies as to the nature of the sugars occurring in the leaf are for 

 that reason of greater importance, and for such investigation they used the 

 leaves of Tropaeolum. In what follows we will deal with the results of some 

 of their experiments without discussing the methods they adopted to obtain 

 them. 



116, 1. 36 P. 117, 1. n, for We need not enlarge . . . with these relations. 

 read We need not therefore enlarge on these results. GILTAY (1898) and 

 BROWN (1899) have employed this method in a modified form. They worked 

 with ordinary air whose percentage of CO 2 was accurately determined ; further, 

 they used daylight and introduced only single leaves into the bell-jars, which 

 leaves were still attached to the plant, so more easily guarding against wilt- 

 ing than was possible with severed leaves. GILTAY has experimented with 

 a large number of plants, both European and Indian ; he calculated the value 

 per hour per sq. m. and found it to be from 0-4 g. to 0-8 g. in the former and 

 0-4 g. to 1-4 g. in the latter. Assimilation, therefore, in tropical plants exceeded 

 that in mid-European plants only to an unimportant extent. Exactly the 

 same value, viz. 0-58 g., was obtained for the sunflower, whether grown in 

 Europe or in Java. BROWN obtained quite similar values, and his experiments 

 were published for the first time in detailed form in 1905. He made it out to 

 be in the case of Helianthus 0-4-0-5 g., but in certain other plants it was some- 

 what less ; the maximum occurred in Polygonum, viz. 0-593 g. As we see, 

 GILTAY'S and BROWN'S estimates are much lower than those obtained by 

 SACHS and A. MULLER with the half-leaf method. BROWN, moreover, makes 

 so many adverse criticisms on the half-leaf method that new experiments 

 appear necessary before one can determine whether it can make any claim 

 to accuracy. 



118, 11. 9-10, for study first the amount ... in the air. read study first how 

 the plant manages to acquire the carbon-dioxide. In one of BROWN'S experi- 

 ments (1905) a sq. m. of leaf surface of Helianthus took up 440 ccm. (or roughly 

 \ a litre) of carbon-dioxide in an hour. Our first inquiry must be how much 

 CO 2 there is in the air, and whether the amount present suffices for the needs 

 of the leaves. 



I. 16, after average read in England ; for 2-8 read 2-94 ; after air read 

 (minimum, 2-43 ; maximum, 3-60). 



II. 41-6, for will show. According to SACHS . . . and imagine the read 

 will show (SACHS, 1884). A sunflower has a leaf surface approximately 1-5 

 sq. m. in extent. Taking as a basis the experiment referred to above it would 

 absorb 660 ccm. of carbon-dioxide per hour, equal to about 1-3 g. Hence 



