M. II. V. Molil 071 the Structure of Chlorophyll. 423 



its earlier stages of development, since tlie starch-grains and the 

 green substance of the chloro})hy]l-globulcs by no means exhibit 

 in all cases uiiiform development and equal duration*. 



Especial theoretical interest has attached to the relative con- 

 ditions of starch and chlorophyll, since Mulder (Physiological 

 Chemistry, Edinb. 1819, p. 286) deduced the cause of the excre- 

 tion of oxygen gas by green plants from a conversion of starch- 

 grains into chlorophyll. According to jMulder's view, the starch- 

 grains always furnish the material for the formation of the wax 

 constantly combined with the green colouring matter, and he 

 therefore believes that the formation of the green substance of 

 the chlorophyll-globules (composed of wax and colouring matter) 

 is connected with a gradual transformation, advancing inward 

 from the surface, and finally a c sappearance of the starch- 

 grains. This transformation of the starch into wax would give 

 rise to an abundant excretion of oxygen gas, and hence plants 

 would not exhale oxygen because they are green, but while they 

 are becoming green, since under the influence of light they con- 

 stantly form new colouring matter (probably from protcine), and 

 the wax combined with this from starch. 



It certainly is worth the trouble to investigate how far this 

 theory agrees with the results of anatomical investigation. In 

 reference to this, we have to ascertain, whether starch in all 

 cases precedes chloro])hyll ; whether the form of the chlorophyll 

 is compatible with the assumption of its origin from starch- 

 grains, and whether the increase of the size of the mass of chlo- 

 rophyll is combined with a diminution of that of the starch- 

 grains. 



The solution of the first question is less easy than it appears 

 at first sight, since, from the almost universal diffusion of starch, 

 and the circumstance that young organs, and especially young 

 leaves, are mostly very rich in it, it is not easy to find cells which 

 are free from starch in their earlier stages of development and 

 subsequently produce chlorophyll. I believe, however, that such 



* [We can hai-dly imagine that the <liversities above indicated are regular 

 and constant characteristics of the plants. It seems far more probable that 

 they point to conditions of the nutritive processes in the leaves in question. 

 For we see the chlorophyll-corpuscles of the Confervoid Alga;, as also those 

 of the Mosses, Hepaticic, prothallia of Ferns, &c., passing through these 

 various stages in the same cells. The presence of starch in the chlorophyll 

 uidicates a previous active assimilation of food ; it is accumulated in the 

 Confervoids, &c. as the cells acquire their full size, and especially if these 

 remain loug at rest before dividing; it is dissolved and disappears when the 

 green contents (which at the same time lose much of their granular cha- 

 racter) are about to be converted into zoospores. The starch reappears in 

 the contents of the zoospores soon after they have become encysted and 

 begun to germinate. — A. H.] 



