1899] 



VEGETABLE ANIMATION 



197 



petals are bent back, and the stamens radiate in all directions. The 

 latter are, however, never so far separated naturally but that the 

 slightest irritation will cause them to spread out farther. If a pencil 

 point be applied at the base of a petal, instant divergence of the 



Sparman n ia africana. 



Fig. 3. — Undisturbed, p, petal ; sp, sepal. Fig. 4. — Irritated (uat. size). 



Fig. 5. — A stamen (enlarged). 



stamens ensues, and the petals and sepals bend still farther back. If 

 the stimulus be severe, the expansion of the tissues uniting the bases 

 of the stamens, and the recurving of the petals and sepals, are so great 

 as to give the flower the appearance of being turned outside in. 



The organs return very slowly to the position assumed before 

 stimulation. The swellings on the filaments probably serve the pur- 

 pose of entangling the head of the insect-visitor, and thus securing 

 more decided irritation. The stigma is well exposed when the maxi- 

 mum spread of the stamens is reached. 



The movements exhibited by the androecium of certain composites, 

 notably the corn-flower, have received careful study. If the anthers 

 of a newly-opened floret be touched they are immediately drawn 

 downwards, with a steady motion, by the contraction of the filaments. 

 The pollen, being pressed against the enclosed pistil, wells out for a 

 little at the top of the anther-tube in a steady stream. The stigma is 

 ultimately carried beyond the tube by the elongation of the style. 



In the Stylidiaceae, a family very closely related to the Compositae, 

 we find a remarkable modification of the floral mechanism described 

 above. The stamens in Stylidium (Candollea) are only two in number, 

 and are united with the style to form a trigger-like apparatus, the 

 gynostemium, which hangs outside the flower, and is fixed slightly to 

 a triangular plate — a modified petal — coated with a sticky exudation. 

 r>eing protandrous, the two anthers occupy at first the summit of this 

 bent column, and in a day or two they wither, and the stigma enlarges 



