304 MODIFIED CIROUMNUTATION. Cbap. VI. 



OucurbitacecB. — The cotyledons of Cucurhita aurantia and ovi- 

 fera, and of Lagenaria vulgaris, stand from the 1st to the 3rd daj 

 of their life at about 60° above the horizon, and at night rise up 

 so as to become vertical and in close contact 'with one another. 

 With Cucumis dvdaim- they stood at noon at 45° above the hori- 

 zon, and closed at night. The tips of the cotyledons of all these 

 species are, however, reflexed, so that this part is fully exposed 

 to the zenith at night ; and this fact is opposed to the belief 

 that the movement is of the same nature as that of sleeping 

 plants. After the first two or three days the cotyledons 

 diverge more during the day and cease to close at night. 

 Those of Trichosanthes unguina are somewhat thick and fleshy, 

 and did not rise at night ; and they could perhaps hardly be 

 expected to do so. On the other hand, those of Acanthosicyos 

 horrida * present nothing in their appearance opposed to their 

 moving at night in the same manner as the preceding species ; 

 yet they did not rise up in any plain manner. This fact leads 

 to the belief that the nocturnal movements of the above-named 

 species has been acquired for some special purpose, which may 

 be to protect the young plumule from radiation, by the close 

 contact of the whole basal portion of the two cotyledons. 



Giranium rotundifolium (Geraniacefe). — A single seedling came 

 up accidentally in a pot, and its cotyledons were observed to 

 bend perpendicularly downwards during several successive 

 nights, having been horizontal at noon. It grew into a fine 

 plant but died before flowering : it was sent to Kew and pro- 

 nounced to be certainly a Geranium, and in all probability the 

 above-named species. This case is remarkable because the 

 cotyledons of O. cinereum, Endressii, Ihericum, Bichardsoni, and 

 subcuulescens were observed during some weeks in the winter, 

 and they did not sink, whilst those of G. Ih.ricum rose 27° at 

 night. 



Apium petroselinum (Umbelliferse). — A seedling had its cotj'- 

 ledons (Nov. 22nd) almost fully expanded during the day ; by 

 8.30 P.M. they had risen considerably, and at 10.30 p.m. were 

 almost closed, their tips being only -^ of an inch apart. On 

 the following morning (23rd) the tips were y'^ of an inch apart, 



• This plant, from Dammara climber; it has been doacribod 



Land in S. Africa, is reraiivkablo in ' Transact. Linn. Soo.,' Xiyii 



from being tlie uno known mem- p. 30, 

 ber of the Family which i» not a 



