CiiAr. X. APOGEOTROPISM. 507 



and the upper part to one of the suh-peduncles of 0. mi nosa. 

 The Tipper part bends downwards, after the flower has begun 

 to wither, and the whole peduncle then forms a hook; that 

 this bending is due to epinasty we may infer from the case of 

 0. carnosa. When the pod is nearly ripe, the upper part 

 straightens itself and becomes erect ; and this is due to hypo- 

 nasty or apogeotropism, or both combined, and not to helio- 

 tropism, for it occurred in darkness. The short, hooked part of 

 the peduncle of a cleistogamic flower, bearing a pod nearly ripe, 

 was observed in the dark during three days. The apex of the 

 pod at first pointed perpendicularly down, but in the course of 

 three days rose 90°, so that it now projected horizontally. The 

 , course during the two latter days is shown in Fig. 189 ; and 

 it may be seen how greatly the peduncle, whilst rising, -ciroum- 

 nutated. The lines of chief movement were at right angles 

 to the plane of the originally hooked part. The tracing was 

 not continued any longer ; but after two additional days, the 

 peduncle with its capsule had become straight and stood 

 upright. 



Concluding Bemarlcs on Apogeotropism. — When apo- 

 geotropism is rendered by any means feeble, it acts, 

 as shown in the several foregoing cases, by increasing 

 the always present circnmnutating movement in a 

 direction opposed to gravity, and by diminishing that 

 in the direction of gravity, as well as that to either 

 side. The upward movement thus becomes unequal 

 in rate, and is sometimes interrupted by stationary 

 periods. Whenever irregular ellipses or loops are still 

 formed, their longer axes are almost always directed 

 in the line of gravity, in an analogous manner as 

 occurred with heliotropic movements in reference to 

 the light. As apogeotropism acts more and more 

 energetically, ellipses or loops cease to be formed, and 

 the course becomes at first strongly, and then less and 

 less zigzag, and finally rectilinear. From thip grada- 

 tion in the nature of the movement, and more especially 

 from all growing parts, which alone (except when pul- 

 vini are present) are acted on by apogeotropism, con- 



