317 



potash under closed bell-jars. Corenwinderi found that buds and young 

 leaves do not develop further in air free from carbon-dioxid. In Bous- 

 signault's- experiments two maize kernels developed into plants of which 

 the dry weight itself and the carbon and oxygen contents were less than in 

 the seed, while the nitrogen content was just as large. Hydrogen and ash 

 had undergone a slight increase. Bohm^ found in leaves of the scarlet 

 runner bean, cut off from the plant during growth, from which the starch 

 had been removed by darkness, that these leaves not only formed roots 

 from the petioles in full daylight and in an atmosphere containing carbon- 

 dioxid, but also increased in breadth even if they were watered only with 

 distilled water. On the other hand the seedlings of the scarlet runner bean 

 grown in distilled water and exposed to the action of full daylight under 

 bell-jars with caustic potash showed only an increase in length up to lo cm. 

 while the stems shrivelled below the primordial leaves which as a rule were 

 free from starch. Seedlings of the scarlet-runner bean which had been 

 grown in garden soil rich in humus but were robbed of all but a small 

 amount of their starch by weak illumination, did not form any new starch 

 but went to pieces when later strongly illuminated in an atmosphere robbed 

 of its carbon-dioxid. Therefore, the carbon-dioxid in the soil and the other 

 favorable conditions for growing were of no value. Godlewski* found that 

 the starch also disappeared in plants exposed to full daylight if the carboa- 

 dioxid of the air was kept from them. 



A further insight into the method of growth of plants from which the 

 carbon-dioxid of the air had been removed is given by my own experiments''. 

 Young cabbage plants were left in a 0.5 per cent, nutrient solution, part 

 under bell-jars with caustic potash, part under others without caustic potash 

 and the remainder left free between the bell-jars. After ten days the har- 

 vest yielded : — 



Bell-jars Bell-.iars 



Uncovered plants with Potash without Potash 



Plant No I. 11. III. IV. V. VI. VII. VIII. IX. 



Fresh weig-ht of root and 



stem 0.457 0.367 0.414 0.470 0.17.5 0.2305 0.297 0.313 0.232 



Fresh weig-ht of leaves . . 1.598 1.494 1.564 1.682 0.765 1.011 1.736 1.712 1.850 

 Upper leaf surface in 



square cm 50.6 47.5 50.1 47.3 25 4 26.6 50.4 54.1 37.1 



Total dry weight 0.2755 0.2510 02.685 0.2760 0.0760 0.0985 0.1705 0.1740 0.1765 



Percentage of the fresh 



weight in dry weight 13.4 13.5 13.5 12.8 8.4 7.9 8.1 8.6 8.4 



Total evaporation in 



grams 69.3 74.4 82.5 75.0 27.4 34.4 43.1 40.4 43.3 



Evaporation per gram 



dry weig-ht 251.5 296.4 307.2 271.7 360.6 349.2 252.8 232.2 245.3 



The table shows that the production in fresh and dry weight was the 

 smallest under the bell-jars with potash. The absolute amount of evapora- 



1 Recherches chimiques sur la vegetation. Fonctions des feuilles. Compt. rend, 

 t. LXXXII, 1876, No. 20, p. 1159. 



- Boussingault, Vegetation du Mays, commence dans une atmosphere excempte 

 d'acide carbonique. Compt. rend. Vol. LXXXII, No. 15, p. 788. 



•■! Biihm, in Sitzungsber. d. Wierner Akad. 1876, cit. Bot. Zeit. 1876. p. 808. 



■i Bibliographische Berichte iitaer die Publikationen der Akademie der Wissen- 

 schaften in Kraukau. Part I, cit. Bot. Zeit. 1876, p. 828. 



5 Sorauer. Studien iiber Verdunstung. Forschungen auf dem Gebiete der 

 Agrikulturphysik, Vol. Ill, Parts 4 and 5. 



