CRUCIFERAE 



117 



291. B. laevigata L. (Herm. Miiller, ' Alpenblumen,' pp. 148-9.) The flowers 

 ire aggregated into conspicuous inflorescences. Outside the base of each short 

 itamen there is a nectary, the secretion of which collects in the cavity of the sepal 

 mmediately below it. There is a non-secreting nodule outside the base of each pair 

 )f long stamens. Each petal possesses a basal lobe each side, the one on the side 

 lext the short stamen being considerably larger than the other, and thus serving as 

 t nectar-cover for the functional nectaries, leaving free but a small passage to the 

 ecretion. The reduction of the other lobes of the petals is correlated with the 

 'estigial condition of the remaining nectaries. 



The anthers are so placed that every insect approaching the nectar must on 

 .hree sides touch a dehisced anther, and on the fourth come into contact with the 

 .imultaneously mature stigma. An insect passing from flower to flower will therefore 

 continually effect cross-pollination. Failing insect-visits, the anthers and stigma are 



Fig. 35. Biscutella laevigata^ L. (after Herm. Miiller). A. Flower after removal of two sepals and 

 two petals : seen from the side. B. Petal seen from the inner side. C. A short stamen with the two 

 adjacent petals ( x 7). a, one of the lower sepals with a cavity (b) in its base, which serves as a nectar 

 reservoir ; c, functional nectary ; d, vestigial nectary ; e, the two short stamens, which dehisce introrsely ; 

 _/j the four long stamens, which dehisce towards the short ones ; g, one of the upper sepals ; A, petals; 1, 

 ovary ; k, style ; /, stigma ; m, larger lobe of a petal ; n, smaller lobe of a petal ; 0, entrance to the nectar. 



Drought into contact by the closing of the flower, so that automatic self-pollination 

 ensues. 



Visitors. Herm. Miiller observed 23 flies, 5 Hymenoptera, 6 Lepidoptera, and 

 Meligethes in the Alps. Loew noticed one of the Pyralidae, skg., in Switzerland 

 V Beitrage/ p. 56). 



88. Lepidium L. 



Small white or yellow flowers, homogamous or protogynous, with half-concealed 

 nectar. Four or six nectaries. The corolla is sometimes absent. 



292. L. Draba L. (Kirchner, Flora v. Stuttgart,' pp. 308-9 ; Kemer, ' Nat. 

 Hist. PL' Eng. Ed. 1, I, p. 432.) The small white flowers are not individually 

 conspicuous, but many of them are aggregated together. In favourable weather 

 the flower opens so widely at the beginning of anthesis that its diameter is 6-7 mm., 



