152 



Phaseolus multiflorus. Vicia sativa, Lepidium sativum and 

 Sinapis alba — and so arranged the containing vesscls 

 that their open ends dipped into potash solution. After 

 36 to 48 hours the potash reached its highest level so 

 that ail the oxygen had been absorbed. Up to this time 

 the whole apparatus had stood in the dark, but then the 

 seedlings were illuminated unilaterally. There was still no 

 trace of curvature to be seen even after several hours. 

 If he allowed air to enter, then the commencement of the 

 curvature was already visible after one hour. He therefore 

 concluded, that no heliotropic phenomena are observable 

 without free oxygen. 



W ortmann^) in his investigation on intramolecular 

 respiration made the statement that ail irritabelity is lost 

 in an oxygen-free atmosphère, but that even in the case 

 of plants which hâve for weeks been deprived of oxygen, 

 irritabelity returns on renewed access of oxygen, A very 

 small portion of his investigation is concerned with the 

 geotropic sensitiveness of seedlings. He placed the ger- 

 minating seeds of Vicia Faba, Phaseolus vulgaris and 

 Phaseolus multiflorus in absorption tubes of 100 ce. 

 capacity of which the openings were in contact with 

 mercury covered with a layer of water. The seeds remained 

 for several days in this enclosed space till a distinct 

 increase in volume had taken place. Then ail the oxygen 

 had been used up. Roots germinating in a horizontal 

 position now showed no geotropic curvature. He got the 

 same négative results with parts of the stem of Paeonia 

 peregrina. Wortmann did not understand why the 

 intramolecular respiration is not a source of energy to 

 the plant capable of furnishing the forces which bring 

 about growth. 



') }. Wortmann. Ueber die Beziehungen der intramolecularen zur 

 normalen Athmung der Pflanzen. Àrbeiten des Bot. Inst. in Wiirzburg 

 II. 1880, p. 509. 



