No. 4.] MASSACHUSETTS WEEDS. 271 



list of all naturalized and adventive species. Some of these 

 have also, in other sections of the State, become decidedly 

 common. 



Methods by which Weeds are Disseminated. 



There are many methods by which weeds are disseminated. 

 Besides the natural method, which includes the various 

 methods of propagation characteristic of the plants, there are 

 many artificial methods, dependent very largely upon human 

 agencies. Besides being dependent upon seeds, there are 

 many plants, including some of the weeds as well, which 

 propagate themselves by means of root-stalks or underground 

 stems, runners and running roots. Examples of propagation 

 by root-stalks or rhizomes are furnished by the flag-root, 

 blue iris and some ferns ; while in the weeds we find a good 

 example in the couch-grass. Plants which possess this habit 

 are wonderfully tenacious and are the most difiicult to eradi- 

 cate. Golden hawk weed is propagated by runners similar to 

 the strawberry, and the Canada thistle by running roots. 

 These methods of propagation are, however, merely acces- 

 sory methods. 



The most universal method of plant propagation is by 

 seed, and the many ingenious ways in which plants are able 

 to disseminate themselves is remarkable indeed. One could 

 hardly have ever seen a dandelion without having observed 

 the admirable seed apparatus, the seed being constructed 

 especially for being wafted by the wind. No less interesting 

 as wind propagators are prickly lettuce, milkweed, Canada 

 thistle and fire-weed. 



Another method of seed propagation common to some 

 weeds is by animals. Many plants, such as the poke weed, 

 have berries which are eaten by birds, and as most hard seeds 

 are not digested by them they are dropped here and there. 

 If conditions are favorable they will readily develop. Many 

 seeds eaten by horses and cattle are not impaired, and in this 

 manner many weeds find new abodes. Then again we find 

 curious devices connected with seeds for attachino; themselves 

 to animals. There are many of these devices ; one of the 

 best-known plants among us which has acquired this habit is 

 the burdock. 



