518 MODIFIED CIECUMNUTATION. Chap. X 



the prostrate habit of Helianthemum prostratum " brings the 

 capsules in contact with the surface of the ground, postpones 

 their maturity, and so favours the seeds attaining a larger size." 

 The capsules of Cyclamen and of Oxalis acetosella are only occa- 

 sionally buried, and this only beneath dead leaves or moss. If 

 it be an advantage to a plant that its capsules should be kept 

 damp and cool by being laid on the ground, we have in these 

 latter cases the first step, from which the power of penetrating 

 the ground, with the aid of the always present movement of 

 circumnutation, might afterwards have been gained. 



Araclm hyp^gcea. — The flowers which bury themselves, rise 

 from stiff branches a few inches above the ground, and stand 

 upright. After they have fallen off, the gynophore, that is the 

 part which supports the ovarium, grows to a great length, even 

 to 3 or 4 inches, and bends perpendicularly downwards. It 

 resembles closely a peduncle, but has a smooth and pointed 

 apex, which contains the ovules, and is at first not in the least 

 enlarged. The apex after reaching the ground penetrates it, in 

 one case observed by us to a depth of 1 inch, and in another 

 to 0'7 inch. It there becomes developed into a large pod. 

 Flowers which are seated too high on the plant for the gyno- 

 phore to reach the ground are said * never to produce pods. 



The movement of a young gynophore, rather under an inch 

 in length and vertically dependent, was traced during 46 h. by 

 means of a glass filament (with sights) fixed transversely a 

 little above the apex. It plainly f.ircumnutated (Pig. 193) 

 whilst increasing in length and growing downwards. It was 

 then raised up, so as to be extended almost horizontally, and 

 the terminal part curved itself downwards, following a nearly 

 straight course during 12 h., but with one attempt to circum- 

 nutate, as shown in Fig. 194. After 24 h. it had become nearly 

 vertical. Whether the exciting cause of the downward move- 

 ment is geotropism or apheliotropism was not ascertained; but 

 probably it is not apheliotropism, as all the gynophores grew 

 straight down towards the groand, whilst the light in the hot- 

 house entered from one side as well as from above. Another 

 and older gynophore, the apex of which had nearly reached the 

 ground, was observed during 3 days in the same manner as the 

 first-mentioned short one ; and it was found to be always oircum- 

 nutating. During the first 34 h. it described a figure which 



* 'Gard. Clironicle,' 1857, p. 



566. 



