64 PLANT LIFE. 



below the surface, it is well adapted to the conditions 

 of agriculture. The uppermost parts catch in the teeth 

 of the grubbers and harrows, and are actually spread 

 abroad by the machines employed to eradicate them. 

 The Autumn Crocus has an entirely different arrange- 

 ment. The base of the stem swells out into a fleshy 

 solid body (botanically a '^conn") packed with a reserve 

 supply of plant food. Flowering takes place on the 

 strength of this food, which has been prepared the year 

 before ; after flowering, the leaves go on manufacturing 

 sugar, and the rudiments of the new corm may be seen 

 on one side of and a little below the old one, which is 

 now becoming withered. Every year the new corm is 

 formed in this way a little below and to one side of 

 last year's, so that the roots exploit new ground every 

 season. The plant therefore travels sideways and 

 downwards, and eventually reaches a depth of 20 

 centimetres, after which it wanders horizontally without 

 going any deeper. Even the Common Potato has an 

 efficient system. The new tubers are form.ed on 

 underground branches at some distance from the 

 parent ; there are many of these tubers arranged all 

 round the original plant, so that, if all were allowed 

 to develop as they liked, a circle of potato plants 

 would be formed every year. Many other common 

 weeds possess extremely perfect methods of spreading 

 by branches or rhizomes, e.g. Ranunculus repens, Ranun- 

 culus ficaria (which has a quantity of very small 

 potato-like tubers), Trifolium repens, and the Couch 

 Grass, which last can form runners 10 to 16 feet in 

 length. 



In most of the cases mentioned, new and untouched 

 parts of the soil are reached by a special branching or 

 special direction of growth. But sometimes the plant 



