THE COMMON ARUM 



the central portion, and then swells out again 

 forming an oval-shaped sac, as is well shown in 

 the illustration. Now, having obtained such a 

 bloom, cut a tiny portion from the substance of 

 the sac with a sharp penknife, so as to make a 

 small hole. Then turn the hole towards the sun- 

 light and watch what happens. Through the 

 opening will come a tin}^ midge-fly, which at once 

 takes to its wings and disappears from view. Its 

 place, however, is immediately taken by another 

 fly, and presently, still others appear, until at last 

 a veritable army of midge-flies is trooping through 

 the hole. It is rarely that one can find a fully- 

 developed arum without its army of tiny midges 

 within. How came these flies there, and what 

 are they doing ? These are questions I will 

 endeavour to answer later ; meanwhile we have 

 to learn something of the early history of the 

 plant. 



The arum plant, as we know it, may start life 

 from a seed, but it more often develops after the 

 manner of the cultivated potato, and, instead of 

 producing a new plant, simply continues the 

 growth of the old one by means of underground 

 tubers. For, of course, a potato is not a seed, but 

 simply a swollen end of an underground stem, 

 bearing buds, so that when a ^^new" plant is 

 produced from it, it is really the continuation of 

 the growth of the original plant, growth having 

 been deferred at the tuber or potato stage. Such 

 a plant may be likened to the ^' new " plants pro- 

 duced by the runners of the strawberry, which are 

 D 33 



