438 ME. F. DABWIN ON" THE POSITION OF 



and showing the existence of a power of moving towards the 

 front of the transverse plane. On Nov. 4th it was —30° at 

 noon, and it only rose to +2° by 11 p.m. ; and on Nov. 6th it 

 was still —25° at 12.50 p.m. Leaf i. was, on Nov. 6th, at 12.50 p.m. 

 at -40°. 



These facts show that the leaves of the bean are not able to 

 remain at right angles to light while rotating on the klinostat ; 

 but the length of time required to drive back the leaves behind the 

 diaheliotropic plane shows that there is a tendency to remain in 

 that plane in spite of the absence of apogeotropism. 



In another similar experiment the two leaves under observation 

 were— i. at +48°, ii. at +57°; and the plant was then (Oct. 29th, 

 4.5 p.m.) placed in the zenith position at a north window which 

 had no oblique mirror. On Nov. 8th, 10.13 a.m., it was found that 

 the stem had become able to bend so that the leaves did not occupy 

 the same positions with regard to the transverse plane in all parts 

 of the revolution. The two extreme positions were— for leaf i. 

 —8° and -20°, for ii. +15° and 20°. The stem was then tied 

 to a new support, so that (i.) was at -8°, (ii.) at -5°. The same 

 evening (Nov. 8th) the leaves rose to +31° and +33° ; and next 

 day at 12.30 p.m. they were both at +12°. They may therefore 

 fairly be said to be still approximately in the diaheliotropic plane 

 after eleven days on the klinostat. It should be remarked that 

 experiments made at this time are not satisfactory, since the plants 

 do not receive a normal amount of light. 



Experiment with the Vegetable Marrow (Cucurbit* ovif era). 



On Nov. 1st, 10.11 a.m., a seedling whose hypocotyl was 7 

 centim. m length, was placed in the zenith position on the klino- 

 stat in the greenhouse. The cotyledons (called left and right) 

 were both in front of the transverse plane, left +15°, right +45°. 

 On Nov. 10th, 11.20 a.m., the cotyledons were curled backwards 

 epinastically, the main part of the left cotyledon was +35°, and 

 the chord made by the right one was at +20°. On Nov. 16th, 

 9^20 a.m., the left cotyledon was +10°, the right +13°. Thus 

 after fifteen days on the klinostat the cotyledons were approxi- 

 mately at right angles to the light. 



Experiment with the Plantain (Plantago media). 

 A plant growing in a box was placed in dull light for three or 

 four days ; and on July 2, 6.40 p.m., the angles made by the chords 



