HABITS OF WEEDS 89 



or horizontally as circumstances dictate, as in thistle, horse- 

 tail, and coltsfoot. In either case buds are formed which push 

 up above the soil and develop into green shoots, producing 

 leaves and flowers. The food stored underground during the 

 winter is used to start the buds into activity in the spring, and 

 later on the green shoots form an extra stock of food and 

 pass it down below to be stored for the next winter, thus 

 completing the vicious circle. Dormant buds are plentiful on 

 the rhizomes, and if a small piece of the latter is broken off 

 the buds develop, roots and shoots are sent out, and a new 

 plant results. The rhizomes enable the weeds to migrate con- 

 siderable distances, and when great efforts have been made to 

 clear a particular spot it is no unusual occurrence to find the 

 pest turning up many yards away, perhaps in another field, to 

 which it has travelled and escaped notice. 



Coltsfoot is slightly different in habit from the other weeds 

 in this class. Early in the spring, about February, clusters of 

 flower buds are pushed above ground, which give rise to the 

 familiar yellow flowers, somewhat resembling small dandelions. 

 No leaves are produced at this tjme, but when flowering is 

 nearly or quite over more buds develop from other parts 

 of the rhizomes, and this second set produces the large 

 cottony leaves that often carpet the ground where coltsfoot is 

 abundant This separation of flower and leaf leads many 

 people into the mistake of thinking that they are not connected, 

 and too often the flowers are allowed to ripen seed with im- 

 punity by the very farmers who make determined onslaughts 

 on the plant when the leaves have appeared. 



(7) Climbing and Scrambling Weeds. A few plants pro- 

 duce very long, weak stems, which raise themselves into the 

 light and air by twining or scrambling round other vegetation. 

 When these weeds are plentiful among crops they are most 

 troublesome, because they tend to strangle the crop plants and 

 prevent the latter developing properly, and also, if the stems 

 of cereals are weak, the climbing weeds pull them down and 

 cause them to " lodge " without any opportunity of rising again. 

 The worst climbing weeds in this class are convolvulus (or 

 bindweed) and black bindweed. The former is a perennial, 

 with long twisted rhizomes from which an abundance of weak 

 aerial stems are given off, while the latter is an annual whose 

 leaves bear such a similarity to those of the true bindweed that 

 the two weeds are often confused. Both are very leafy, and 

 when they occur abundantly in corn crops it is necessary to 



