FORMATION OF STARCH-GRAINS IN THE CHLOROPHYLL. 311 



cases not starch, but fat, was refuted however by Holle and Godlewski\ who 

 showed that, even in these plants, the decomposition of carbon dioxide yields 

 a volume of oxygen equal to that of the carbon dioxide employed, which could not 

 possibly be the case if fat were immediately formed ; and that under particularly 

 favourable conditions of assimilation — viz., on supplying larger quantities of carbon 

 dioxide to the surrounding air, and using a stronger light — starch can actually 

 be detected in the chlorophyll. It thus appears that in many plants the starch 

 produced in the chlorophyll may be at once transformed into fat, as may also 

 be the case with some species of Vaiicheria : this process presents nothing 

 at all surprising, since I showed so long ago as 1859 and later, by numerous 

 examples ^ that the transformation of fat into carbo-hydrates and of carbo-hydrates 

 into fat, is a very common phenomenon in plants ; and with respect to the 

 glucose in Allium, it is simply to be noticed that it matters little for the plant 

 whether the chemical processes produce starch or sugar, as we shall see again in 

 the following lecture. 



The formation of starch in the chlorophyll may be more easily observed in 

 the simply organised Algae than in the leaves of the higher plants. Kraus found, 

 in 1867, that in Spirogyra, previously kept in the dark and thus deprived of 

 starch, the formation of starch was to be recognised, on illuminating it under the 

 microscope, even after five minutes in direct sunlight, and in the course of two 

 hours in diffused daylight ; and similar results were obtained with the leaves of 

 a Moss {Funarid), and the water-plant Elodea. It being, further, established that 

 assimilation is much more energetic in yellow than in blue light, Famintzin also 

 succeeded in demonstrating, in 1867, that starch is formed more rapidly under the 

 influence of yellow than of blue light. 



Although my above-cited researches (collected in my Ex per imcjital -physiologic) 

 admit of no doubt that starch, or a substance equivalent to it, is to be regarded 

 as the first visible product of assimilation, it was nevertheless a welcome con- 

 firmation of my theory when Godlewski, in 1873, demonstrated, by experiments 

 as ingenious as they were simple ", that in an atmosphere devoid of carbon dioxide 

 no starch is produced in the chlorophyll-corpuscles, even in the light. He also found 

 that the starch produced in the chlorophyll disappears, not only in the dark but 

 even in intense light, when the surrounding air contains no carbon dioxide. Of 

 particular importance is the fact, established by Godlewski, that on increasing the 

 amount of carbon dioxide contained in the air to 8%, the formation of starch is 

 four or five times more energetic in a strong light, while in diff'used light the action 

 is much feebler. Very large quantities of carbon dioxide in the air, however, 

 prevent the formation of starch ; and the more so the feebler the light *. These 

 statements are the more valuable since Godlewski had previously established. 



' Emil Godlewski, in Flora, p. 215, and Holle, ibid., p. 113. 



"^ Sachs, ' Uebcr das Auftreten der Stärice bei Keimung öllialtiger Samen^ Bot. Zeit. 1859, 

 p. 177. 



=* Godlewski, ' Abliängiglieit der Stärliebildung in den CJilorophyllJwrnern von dem Koiilen- 

 säurcgeiialt der Luft.'' Flora, 1873, p. 378. 



* Godlewski, 'Abliängiglieit der Sauerstoffabscheidung der Blätter von dem Koldensäuregehalt 

 der Luft.' Arbeiten des bot. Inst, in Würzburg, 1873. Bd. I, p. 343. 



