" COMPOSITE 249 



flowers open at 6 a.m. and close between 4 and 5 ; while 

 at Innsbruck, Kerner found them opening about 7 to 8 

 and closing at 6 to 7. The plant is scabrous and hairy. 

 H. glabra, on the other hand, is glabrous ; while 

 H. radicata has the leaves rough, with stiff hairs. 



Lactuca (Lettuce) 



There are but few florets in each flower-head. The 

 achenes taper into a slender beak, and have a pappus of 

 many white silky simple hairs. There are four British 

 species : L. muralis has the beak shorter than the 

 achene, and leaves on long stalks ; in L. virosa and 

 L. Scariola the beak is about as long as the achene ; in 

 L. saligna, twice as long. 



L. Scariola. — The plant is glabrous, but with a few 

 stifi" bristles or prickles on the edges and midribs of the 

 leaves in the lower part of the plant, and on the stem. 

 This is a shade-loving species, and the leaves are very 

 delicate. While most English plants have the leaves 

 so arranged as to receive a maximum of light, in this 

 species they change their position so as to avoid it. 

 In the morning and evening, when it is faint, they are 

 ranged perpendicularly to it, i.e. east and west. When, 

 however, the sun becomes strong they turn themselves 

 north and south, so as to receive as little light as possible. 

 For the same reason they are horizontal in the shade, 

 more or less perpendicular in sunshine. The involucral 

 scales ai;e smooth, tense, and full of a sticky juice. The 

 investing membrane is so delicate that it is pierced by 

 the claws of insects, such as ants, which thus become 

 smeared by the sticky juice. The result is that they do 

 not attempt to reach the flowers. It is a rare plant in 

 waste places in some of our southern and eastern counties. 



L. virosa, a commoner plant, is closely allied to the 

 above, but is never generally scabrous. 



SONCHUS (Sowthistle) 



Achenes not beaked ; pappus sessile, of numerous 

 simple hairs ; leaves clasping the stem at the base. 



