UMiir or c.uowiii is i' lasts 327 



phml upon one another, and the ver)' distinct habit 

 (jf associatint^ together that they may attain some 

 end such as the visits of insects, leads us to con- 

 sider two other aspects of plant-hfe, both of which 

 are so full (jf interest that wo botanical work can 

 now be considered complete without some reference 

 to the matter. If we carefully dig up a clover 

 [jlant or a broad bean and examine the little njot- 

 lets we shall observe some small knobs or swellings 

 upon them. These swellings are onh' found here 

 and there on some oi the roots, so that their 

 presence is not a normal condition. Placing one of 

 these knobs under a powerful microscope, we shall 

 find it to be not ordinary root tissue but a substance 

 teeming with countless numbers of rod-like or 

 rounded atoms which botanists who have investi- 

 gated the subject tell us are bacteria, />., incon- 

 ceivabl)' small one-celled plants which are often 

 the cause of terrible diseases. But some of these 

 mysterious organisms, on the other hand, are 

 capable of beneficial results. It has of late been 

 clearly proved that leguminous plants having these 

 colonies of bacteria on their roots possess the 

 power of assimilating the free nitrogen that forms 



