VITALITY OF SEEDS 23 



hood of towns upon empty building plots. Such a 

 weed-distributing area is well shown in the photograph 

 (Fig. 2). All weeds on such spaces should be cut as 

 regularly as elsewhere. 



SEEDS PRODUCED BY VARIOUS WEEDS 



In view of what has been said about the manner in 

 which weeds are spread, it is interesting to give a few 

 notes on the number of seeds produced by a single 

 flower or plant of various weeds. Below (p. 24) is a table, 

 from which it may be seen at a glance that many weeds 

 produce a prodigious number of seeds, affording a strik- 

 ing example of the harm a single plant may do. With 

 such prolific plants one need no longer wonder at the 

 rapid increase and distribution of weeds when no care 

 is taken to keep them within bounds. The number of 

 seeds largely depends on the size of the plants examined. 

 The different figures given for the same plant are the 

 result of separate investigation by different authors. 



THE VITALITY OF SEEDS 



Prevention of seeding of weeds is especially important 

 in view of the fact that many seeds possess great 

 Vitality, and are able to live on in the soil under what 

 might be considered adverse conditions. One of the 

 best known cases is that of Charlock (see p. 58), the 

 seeds of which may lie dormant in the soil for many 

 years. De Candolle * believed that if seeds are buried 

 sufficiently deeply in the soil, where they would be 

 well and continuously protected from the great in- 

 fluence of moisture and oxygen, their vitality would be 



1 Physiologic Vegdtale, tome xi. p. 618. Paris, 1832. 



