Papaver alpinum.—­H.  Hoffmann (’Speciesfrage’ 1875 page 47) states that this species produced seeds capable of germination only on one occasion.

Corydalis cava (Fumariaceae).—­Sterile:  see the previous discussion on self-sterile plants.

Corydalis solida.—­I had a single plant in my garden (1863), and saw many hive-bees sucking the flowers, but not a single seed was produced.  I was much surprised at this fact, as Professor Hildebrand’s discovery that C. cava is sterile with its own pollen had not then been made.  He likewise concludes from the few experiments which he made on the present species that it is self-sterile.  The two foregoing cases are interesting, because botanists formerly thought (see, for instance, Lecoq, ‘De la Fecondation et de l’Hybridation’ 1845 page 61 and Lindley ‘Vegetable Kingdom’ 1853 page 436) that all the species of the Fumariaceae were specially adapted for self-fertilisation.

Corydalis lutea.—­A covered-up plant produced (1861) exactly half as many capsules as an exposed plant of the same size growing 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, notwithstanding 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 undisturbed flowers contained fifty-three seeds; whilst nine capsules 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 separated; and, on a second occasion, forty-one out of forty-three flowers were in this state.  Hildebrand states (Pring.  Jahr. f. wiss.  Botanik, B. 7 page 450) that the mechanism of the parts in this species is nearly the same as in C. ochroleuca, which he has fully described.

Hypecoum grandiflorum (Fumariaceae).—­Highly self-sterile (Hildebrand, ibid.).

Kalmia latifolia (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.”