86 WONDERS OF PLANT LIFE 



of green tufts can be sent up to replace those which 

 have been torn away. In the case of the Ground- 

 sel or Chickweed the continuance of the race is 

 assured by the facility with which the little plant 

 can reproduce its kind. Both these species seem 

 to be harmless and sweet-tasting, such as the 

 larvae of insects, as well as snails and slugs, would 

 delight to feed upon. Yet it is well known that 

 these plants are among the most troublesome pests 

 of our gardens. This is simply owing to the fact 

 that both the Groundsel and the Chickweed come 

 to maturity so quickly, that it is not an uncommon 

 thing for several generations to be brought to 

 perfection in a single season. 



The entire animal kingdom lives at the expense 

 of the vegetable world, and to protect the plant 

 against the aggressors many remarkable devices 

 have been called into being. One of the most 

 widespread contrivances for the defence of the 

 plant is the thorn. These spines are very prevalent 

 among many genera, and in the different species, 

 represent modifications of both leaves and stems. 

 The development of the thorn is seen to a remark- 

 able extent in the case of the Cacti, plants which 

 in some ways are more perfectly protected than 

 any others in the world. With many species, 

 particularly among the groups Echinocactus and 



