CREEPING THISTLE, CORN-THISTLE 595 



the last in general appearance, but possesses only a slight odour, 

 and the receptacle is without scales. 



Com Marigold {Chrysanthemum segetum L.). — An annual 

 growing about a foot or eighteen inches high, with yellow flower 

 heads resembling the single common marigold of gardens, about 

 I J or 2 inches across. The upper deeply serrated or lobed leaves 

 partially clasp the stem, the lower ones have petioles, and are 

 pinnatifid. The stem and leaves are smooth, and have an ashy- 

 grey surface. 



The thin flat " seeds " blow about from field to field, and are 

 apt to lie dormant for some time, as charlock seeds do. Clean 

 seed corn and hand-weeding, coupled with ordinary tillage, 

 reduces it. 



Groundsel (Senecio vulgaris L.). — A very common annual on 

 cultivated and waste ground. From 6 to 12 inches high, its 

 stems are furrowed and bear half-clasping pinnatifid leaves. Its 

 flower heads are composed of a number of small yellow flowers 

 which ripen quickly and are distributed by the wind. Each 

 plant keeps on flowering during several months of the year, and 

 it is usual in spring and summer to find heads in all stages of 

 development upon the same plant. 



Cornflower, Com Bluebottle, Hurt-sickle {Centaurea Cyanus 

 L.). — An annual or biennial, now frequently grown as an 

 ornamental plant in gardens, from i to 3 feet high, with entire 

 narrow, lanceolate leaves, which are cottony beneath. When old 

 the stems are hard. The flower heads have an outer spreading 

 ring of bright blue flowers, and ultimately produce oval fruits 

 which are crowned with a ring of short orange-coloured bristly 

 hairs. 



Creeping Thistle, Corn-thistle {Cnicus arvensis Hoff"m). — A 

 perennial with a deeply-seated underground stem, which grows 

 horizontally and sends out shoots upwards into the air. The 

 latter are from 2 to 4 feet high, and bear leaves which are 

 lanceolate, very spinous, and wavy at the edges. The stem has 



