II SCROPHULARIACE.E 317 



the extremity of the flower is a small orifice, suited to 

 the narrow proboscis of a butterfly, and nearer the 

 middle a second and larger one, for that of a humble bee. 

 The corolla gradually elongates, and thus carries the 

 anthers up to the stigma, so that in the absence of 

 insect visits the flower fertilises itself This is more 

 especially the case in certain flowers which are smaller 

 than the others, thus presenting a first stage in the 

 direction of cleistogamy. The stem is quadrangular, and 

 bears narrow opposite leaves. The capsule included in 

 the bladdery calyx -tube suggests a rattle, whence the 

 popular name of the plant — Yellow Eattle. 



Bartsia 



Semi-parasitic herbs. Flowers homogamous or pro- 

 togynous, adapted to humble bees, and containing nectar 

 secreted by the under part of the ovary. There are 

 three British species : B. viscosa, with yellow flowers ; 

 B. Odontites, with flowers in panicled spikes, and pink ; 

 and B. alpina, with dull purple flowers in simple 

 short spikes. 



B. alpina. — The flowers are slightly protogynous. The 

 mode of fertilisation in some respects resembles that of 

 Melampyrum pratense, but the position of the stigma 

 and anthers that of Rhinanthus Crista-galli. When the 

 flower opens the corolla-tube has a length of 12-16 mm., 

 and the pistil projects beyond it. Gradually the tube 

 elongates to 19-20 mm., while the pistil remains almost 

 stationary, so that the anthers are carried close to the 

 stigma. After the stigma has shrivelled up the dry 

 pollen may still be carried by the wind in small clouds, 

 and may serve to fertilise another flower. This species 

 not only derives some nourishment from the earth and 

 some parasitically from other plants, but it also puts the 

 animal kingdom under contribution and is insectivorous. 

 The subterranean winter buds bear scales which leave 

 recesses between them (Figs. 203, 204). These bear 

 glands of two kinds (Fig. 205) somewhat resembling 

 those of Lathrsea (p. 303), and probably with the same 



