CHAP. X. PLANTS STERILE WITHOUT INSECT- AID. 359 



instance, Lecoq, ' De la Fecondation et de 1'Hybridation, 

 1845, p. 61, and Liudley, 'Vegetable Kingdom/ 1853, p. 436) 

 that all the species of the Fumariacese were specially adapted 

 for self-fertilisation. 



C. lutea. A covered-up plant produced (1861) exactly half as 

 many capsules as an exposed plant of the same size grow- 

 ing close alongside. When humble-bees visit the flowers 

 (and I repeatedly saw them thus acting) the lower petals 

 suddenly spring downwards and the pistil upwards; this 

 is due to the elasticity of the parts, which takes effect, as 

 soon as the coherent edges of the hood are separated by the 

 entrance of an insect. Unless insects visit the flowers the 

 parts do not move. Nevertheless, many of the flowers on 

 the plants which I had protected produced capsules, not- 

 withstanding that their petals and pistils still retained their 

 original position ; and I found to my surprise that these 

 capsules contained more seeds than those from flowers, the 

 petals of which had been artificially separated and allowed 

 to spring apart. Thus, nine capsules produced by undis- 

 turbed flowers contained fifty-three seeds ; whilst nine cap- 

 sules from flowers, the petals of which had been artificially 

 separated, contained only thirty- two seeds. But we should 

 remember that if bees had been permitted to visit these 

 flowers, they would have visited them at the best time for 

 fertilisation. The flowers, the petals of which had been 

 artificially separated, set their capsules before those which 

 were left undisturbed under the net. To show with what 

 certainty the flowers are visited by bees, I may add that 

 on one occasion all the flowers on some unprotected plants 

 were examined, and every single one had its petals sepa- 

 rated; and, on a second occasion, forty-one out of forty- 

 three flowers were in this state. Hildebrand states (Pring. 

 Jahr. f. wiss. Botanik, B. vii., p. 450) that the mechanism 

 of the parts in this species is nearly the same as in C. ochro- 

 leuca, which he has fully described. 



FFypecoum grandiflorum (Fumariaceae). Highly self-sterile (Hil- 

 debrand, ibid.). 



l\almia latifolUi (Ericaceae). Mr. W. J. Beal says (' American 

 Naturalist," 1867) that flowers protected from insects wither 

 and drop off, with " most of the anthers still remaining in 

 the pockets." 



Pelargonium zonalt (Geraniaceae). Almost sterile; one plant 



