216 THE STOEY OF THE PLANTS, 



other bulbous plants, several small bulbs are pro- 

 duced each year by the side of the large one, and 

 these smaller bulbs are of course, strictly speak- 

 ing, mere branches of the original crocus-stem. 

 But they grow separate at last, by the decay or 

 death of the central bulb, and themselves in 

 turn produce at their side yet other bulbs, which 

 become the centres of stili newer families. We 

 may parallel these cases with those of trees whose 

 boughs bend down and root in the ground so as 

 to become in time independent individuals ; or 

 with runners like those of the strawberry and 

 the creeping buttercup, which root and grow 

 afresh into separate plantlefcs. 



Sometimes still more curious things happen 

 to plants in the way of reproduction by sub- 

 division. There is an English pondweed, for 

 example, which grows in shallow pools liable to 

 be frozen over in severe winters. As cold 

 weather approaches, the top of the growing 

 shoots in this particular pondweed break off 

 of themselves, much as leaves do at falling time. 

 But they break off with all their living material 

 still preserved within them undisturbed ; and 

 they then sink and ■ retire to the unfrozen 

 depths of the pond, where they remain unhurt 

 till spring comes round again. This is just 

 what the frogs and newts and other animal 

 inhabitants of the pond do at the same time, to 

 prevent getting frozen. Next year the severed 

 tops send out roots in the soft mud of the bottom, 

 and grow up afresh into new green pondweeds. 



It is therefore impossible to make any broad 

 line of distinction in this way between what may 



