PAPA VERA CEA E 67 



have already been robbed of their pollen. As they visit the flowers of an inflor- 

 escence in a systematic manner, working from below upwards, they regularly effect 

 cross-pollination, either geitonogamy or — when passing from one plant to another — 

 xenogamy. 



44. Hypecoum L. 



Protandrous pollen flowers, usually yellow in colour, with large inner petals 

 which conceal the pollen in a pouch. As regards flower-pollination they resemble 

 the Papavereae. Kerner ('Nat. Hist. PI.,' Eng. Ed. i, II, pp. 178, 182) regards them 

 as nectar flowers. 



146. H. pendulum L. — F. Hildebrand (Jahrb. wiss. Bot., Leipzig, vii, 1869-70) 

 states that the two inner of the four petals are provided with a pair of lateral ligules, 

 while the middle part (the actual petal) alters greatly in form during the course 

 of development. The anthers dehisce extrorsely before the flower opens, so that 

 the pollen is received by the inner petals, which at this stage are folded inwards 

 in the form of a spoon. Next the empty anthers shrivel and contract, and the 

 spoon-like petals form a case which completely encloses the pollen. When the flower 

 expands the pollen-pouches open if pressed from above, so that an insect alighting 

 upon one of them must dust its under-surface with pollen. 



During this first stage the stigma is still not quite mature, but after a time 

 the style elongates so as to project beyond the pouches of the petals, and a pollen- 

 covered insect alighting upon the flower must necessarily dust the stigmatic papillae, 

 which are now well developed. Failing insect-visits, the tips and €dges of the pollen- 

 pouches curve somewhat outwards, so that the pollen — if it has not already been 

 removed by insects — is brought into such a position that it can readily fall on the 

 stigma if the plant is shaken, or may be carried to it by the wind. Kerner says 

 that the flowers do not open in bad weather, and that in the closed condition 

 automatic self-pollination (pseudo-cleistogamy) takes place. 



147. H. procumbens L. — Kerner states that the flowers of this species also 

 remain closed in unfavourable weather. 



148. H. grandiflorum L. — Hildebrand asserts that this species is almost 

 always infertile when the stigma is dusted with pollen from the same flower, or 

 another flower of the same plant. 



45. Diclytra DC. 



Homogamous bee flowers, the nectar of which is usually secreted and concealed 

 in two pouches, one at the base of each semi-cordate outer petal. 



149. D. spectabilis DC. (Hildebrand, Jahrb. wiss. Bot., Leipzig, vii, 1869-70 ; 

 Herm. Muller, 'Fertilisation,' pp. 95-6; Knuth, 'Bloemenbiol. Bijdragen.')— The 

 peduncles are so thin and flexible that the flowers always hang perpendicularly 

 downwards by their own weight. The two lancet-shaped sepals fall off very early. 

 Each of the semi-cordate petals encloses three stamens, the filaments of which 

 follow the bend of the outer edge of the petal, and together form a groove on their 

 outer side which leads to the nectar. 



The end of this groove opens exactly where an aperture is left between the 

 outer petals and the winged bases of the inner o.nes, i. e. the two grooves begin 



F 2 



