55G MOTOR SYSTEM 



Among recent investigators, Schwendener, Colling and Schneider 

 all maintain that the dehiscence of anthers is a hygroscopic phenomenon. 

 A strong argument in favour of this view is based by Schwendener 

 upon the fact, that the valves do not begin to curl outwards, until every 

 particle of liquid has disappeared from the cavities of the fibrous cells 

 and the cell- walls have begun to lose water. The following experiment, 

 performed by the author, also suggests that the hygroscopic properties of 

 the cell-walls in the mechanical layer are at any rate partly responsible 

 for the movement of the valves. Transverse sections of air-dried anthers 

 of Tulipa Gcsncriana or Fritillaria imperialis are mounted in a moist 



chamber and examined under the 

 microscope ; the valves, which were 

 widely open in the dry condition, 

 will be seen to curl rapidly inwards 

 in the damp atmosphere, although 

 they are not actually wetted ; this 

 movement is, however, not necessarily 

 hygroscopic in character. If the 

 sections are now exposed to dry air, 

 the valves soon begin to curl out- 

 fio. 226. wards again. It should be stated 



isolated cells of the fibrous layer from the that this opening movement never 



anther-wall of Lilium candidum. A, when i c i 1 



moistened; B, in the dry state; a, outer; proceeds SO tar as to lead to a re- 



i, inner tangential wall. After Steinbrinck, i <> ,1 j. 



semi-diagrammatic. versal of the curvature or even to 



a straightening of the valves. The 

 sections appear quite opaque throughout this experiment, a fact which 

 proves that the cells are filled with air, both during the inward 

 curvature, and while the valves are uncurling. There can therefore be 

 no doubt, that the partial opening of the valves, in this instance, is a 

 purely hygroscopic movement. 



While Kamerling and Steinbrinck undoubtedly go too far when they 

 relegate the whole mechanism of anther-dehiscence to the category of 

 cohesion-movements (cf. the next section), it cannot be denied that co- 

 hesion plays some part in connection with the opening of anther-valves ; 

 it is the quantitative value of this factor which is still uncertain. Co- 

 hesion may actually supply the entire motive power in certain instances. 

 Colling states that this condition is realised in the case of Tacca mac- 

 rantha, Polygala grandis, Sagittaria nutans, and Salvia officinalis. The 

 same investigator, on the other hand, found a hygroscopic mechanism to 

 be present in more than one hundred of the species which he examined. 



