708 



Some Common Thistles. 



[march, 



on damp undrained pastures and sides of ditches (Fig. 2). 

 The root-system of the plant consists of a series of fibrous roots 

 all about the same thickness (Fig. 6). The stem is erect and 

 branched, somewhat slender and soft, with numerous short 

 spines upon its wings. Like its leaves it is a dull green or 

 greenish-purple tint. The flower-heads are small, about i in. 

 in diameter, and bear dark purplish-crimson flowers. The in- 



volucre is practically spineless and similar in colour to the stem. 

 The plant is a biennial. During the first season a compact 

 rosette of leaves is formed close to the ground, from which an 

 erect stem is sent up in the second year. The seeds are pale 

 straw-coloured, and only germinate satisfactorily under the 

 peculiar acid conditions of marshy, damp soil. 



4. The Creeping Thistle {Cnicus arvensis, Hoffm,) is the 

 commonest and most troublesome of all thistles (Fig. 3). It 

 grows abundantly on all sorts of arable land and pastures 

 throughout Europe. It is a perennial plant, exhibiting many 



/ 



Fig. 3. — Creeping Thistle {Cnicus arvensis, Hoffm.). 



