SOME PLANT BIOGRAPHIES. 217 



be considered as modes of individual persistence in 

 the self-same plants, and what may be regarded 

 as modes of reproduction by subdivision. Some 

 plants, like couch-grass and elm, are almost 

 always surrounded by young shoots which may 

 ultimately .become to all intents and purposes 

 independent individuals ; while others, like 

 corn-poppy or Scotch fir, never produce any off- 

 sets or suckers. In the meadow orchids each 

 plant produces every summer a second tuber by 

 the side of the old one ; and from the top of 

 this tuber the next year's stem arises in due 

 time with its spike of flowers. Here we may 

 fairly regard the tuber as a simple means of 

 persistence in the plant itself ; there is nothing 

 we could possibly call reproduction. But in 

 many lilies the older bulbs produce numerous 

 small branch bulbs at their sides; and these 

 younger bulbs may become practically indepen- 

 dent, each of them sending up in the course of 

 time its own stem and its own spike of 

 flowers. 



Even when the main trunk of a tree is dead, 

 through sheer old age, it often happens, as in 

 the elm and birch, that the roots send up fresh 

 young shoots, which may grow again, and 

 prolong the life of the plant indefinitely. In 

 stone-crops and other succulent herbs, which 

 grow in very dry and desert situations, the 

 merest fragment of a stem, dropped on moist 

 soil, will send out roots and grow afresh 

 into a new individual. Cactuses and other 

 desert plants have often to resist innnense 

 drought, and therefore possess extraordinary 



