57 



the granules subsequently originate in it. M. Mohl decides 

 the question in accordance with his observations of nature ; 

 in some cases the chlorophylle is first formed, and the amy- 

 lum granules subsequently developed, as for instance, in the 

 Spirogyrce, Link, and in the Chara, as I have previously men- 

 tioned ; but in other cases the amylum is found first, and then 

 the formation of the chlorophylle takes place. The third case, 

 and which is the most frequent, M. Mohl has not noticed, 

 where the formation of the chlorophylle stands neither pre- 

 viously nor subsequently in connexion with the formation of 

 amylum, where it has for substratum a semi-solid yellowish- 

 white substance which is coloured brown by iodine. 



But even in the Conferva and in the Spirogyrce it may pretty 

 generally be stated that the formation of the chlorophylle pro- 

 ceeds from the amylum ; for it is the amylum granules which 

 are dissolved at the formation of the seed in the Spirogyrte, 

 unite with the green mass present, and produce the substance 

 for the formation of the two membranes which surround each 

 seminal grain of these plants ; they then again condense, and 

 adopt even in the seed a spiral position at the germination of 

 the young plant which proceeds from a prolongation of the 

 third or innermost membrane, but are again employed to pro- 

 duce the substance for the formation of amorphous masses 

 coloured by chlorophylle. What is the physiological object 

 which nature probably attains by this disposition of amylum 

 in leaves ? M. Mohl is rather inclined to answer, that it is a 

 reserved nutriment destined to be employed in those plants 

 which flower but once for the development of the fruit ; and in 

 the perennials, plants losing their leaves in autumn, is carried 

 into the stem and there deposited as material (?) at the expense 

 of which the buds are said to develop in the succeeding spring. 



M. Payen* has prepared lichen starch from Icelandic moss, 

 and after having dried it at a temperature of 100 subjected 

 it to an elementary analysis, which gave C 12 , H 10 , O 5 , a com- 

 position very approximate to the amylum of the higher plants. 

 Great difference in the composition of amylum and moss- 

 amylum was not to be expected ; it was however hitherto ge- 

 nerally supposed that the latter was coloured yellowish-brown, 

 the former blue by iodine ; I have however frequently found 

 * L'lnslitut de 1837, p. 128. 



