SENSITIVENESS OF STAMENS. 4?,?i 



Sachs has given the name Phototonus to the normal motile 

 condition resulting from alternation of clay and night. "A 

 plant in this condition, if placed in the dark, will remain for some 

 time (Irours or even days) in a state of phototonus, which then 

 disappears gradually ; the plant is therefore under normal condi- 

 tions in a state of phototonus even during the night. In the 

 same manner a plant which has become rigid in continued dark- 

 ness retains its rigidity for some time (hours or even days) 

 after being exposed to light. The two conditions therefore 

 pass over into one another onl^- slowlj"." 



1093. Temporary rigidity is produced in the case of the Sensi- 

 tive plant bj- an exposure to a temperature of 15° C. The same 

 effect is produced bj- a temperature above 50^ C, according to 

 Bert's observations at about 60° C. It is stated bj' him that tlie 

 sensitiveness of Mimosa is destro^-ed by exposure to a green 

 light, while plants placed under bell-jars of the following colors 

 remained healtliy : white, red, j-ellow, blue, and violet.^ 



1094. Sensitiveness of stamens. No better illustration of 

 this is afforded than that given b^- stamens of the common Bar- 

 berry. The six stamens lie curved under the arching petals, but 

 if a filament is lightly touched it is jerked suddenly forward, 

 bringing the anther into apposition with the pistil. 



1095. The filaments of certain Compositee are sensitive. The 

 case of the common Chicory has been thus described : The 

 anthers are conjoined to form a tube supported upon five dis- 

 connected filaments which are at first more or less curved out- 

 wards. If the filaments in this condition are lightly touched 

 thej- instantly straighten, carr3ing the anther-tube up a little 

 higher, and thus bringing the pollen all along the stj-le which is 

 enclosed. After a short time thej' resume their former curved 

 condition, retracting the anther-tube to the place which it occu- 

 pied before. It is to be observed that the irritation of a single 

 filament excites onlj' that one, and thus the tube of anthers may 

 be pushed over to one side for a few minutes, again recovering 

 itself after a little while. 



1096. Sparmannia Africana has a cluster of beaded filaments 

 surrounding the pistil and variously intermingled with the sta- 

 mens. When these are touched lightly they open out from the 

 centre with considerable rapidity, and remain thus expanded 

 for a certain period, after which they revert to the closed posi- 

 tion. Somewhat the same phenomenon is to be observed in 



1 Comptes Rendus, Ixx., 1870, p. 339. 



