Exhaustion 



plants which " wear themselves out " by producing 

 seed ; aU the food made and the water absorbed 

 are directed to perfecting parts which are unproduc- 

 tive so far as the individual is concerned. The 

 flowers, fruit, and seeds are either not green at all 

 or consume a far greater quantity of food than 

 their small amount of green tissue enables them to 

 produce. In them the individual actually dies of 

 starvation, starving itself to give its offspring a 

 good start in hfe. Annual and biennial plants are 

 such, and not a few perennials delight us for a time 

 and are no more, for the same cause. Who has not 

 deplored the loss after its brilliant display of such 

 a mule pink as " Napoleon III." ? Yet it is not 

 doomed to die if we prevent it flowering when it 

 wants to, but will then give us plenteous shoots for 

 propagation. So too may the life of annuals be 

 prolonged by restricting their flower production or 

 removing their seed pods before they develop too 

 far. Indeed, in such cold regions as Central Siberia 

 even such confirmed " annuals " as the common 

 shepherd's purse outlive more than one growing 

 season. 



Interesting as this phase of plant -life is, more 

 important to the cultivator is the set of troubles due 

 to external factors such as xmsuitable surroundings 

 and attacks of living agents. A study of the subjects 

 briefly outlined in Chapter I. wiU indicate where 

 there are chances of the surroundings being faulty, 



20 



