78 BRITISH FLOWERING PLANTS chap. 



the honey, but must content themselves with pollen. 

 The seed is oblong, oval,^ much compressed laterally, 

 with the edges produced all round into a thin mem- 

 branous wing, which probably serves for dispersal. The 

 embryo occupies the whole interior. The cotyledons are 

 broadly ovate, entire, flat, and adpressed face to face. 

 They take, therefore, approximately the form of the seed. 

 The Wallflower is a native of Central and Northern 

 Europe, and occurs as an alien, growing on old walls, 

 in this country. 



Barbabea 



B. vulgaris (Winter-cress or Yellow Rocket). — The 

 yellow flowers attain a diameter of -|- inch. The half- 

 concealed honey is produced in abundance by six 

 nectaries, of which the two at the base of the short 

 stamens are often confluent ; it collects in the hollows 

 at the base of the sepals. The insect visitors are bees, 

 flies, and beetles. The leaves are often violet below 

 from presence of anthocyan. The plant, which is very 

 variable, is generally glabrous, but sometimes pubescent. 

 It is widely distributed in the north temperate zone. 



Nasturtium 



The Nasturtium of botanists is, I need hardly say, 

 not the Nasturtium of gardeners, which is a Tropseolum. 

 The true Nasturtiums are annual or perennial, with 

 small white or yellow flowers, and a linear or oblong 

 pod. They live by the side of ponds or streams. 



N. amphibium. — The flowers are yellow. The six 

 nectaries at the base of the stamens form a ring. The 

 anthers of the four long stamens are about on a level 

 with the stigma, and open inwards, so that insects 

 in search of honey touch the stigma with one side 

 of the head, the anthers, or rather one of them, 

 with the other. According to Warnstorf, however, the 

 anthers, as they open, make a half turn, so carrying the 

 pollen away from the stigma, and making self-fertilisa- 



' Avebury (Lubbock), Seedlings, vol. i. 



