HOW PLANTS FLEE FROM THEIR ENEMIES. 27 



The plot of wild asters and goldenrods in like manner has recently 

 suffered much from certain insects working at the roots, at well as at 

 at the tops, and several parasitic fungi have injured some of them. 

 Insecticides have been employed, still, from one cause or another, 

 after a few years, several species have been lost. In some instances 

 it appeared to be due to unfavorable weather. 



A number of species of sunflowers ( Helianthus ) were nearly de- 

 stroyed by rust and mildew, and some patches became nearly extinct, 

 where the roots had slowly fed over the ground. A thrifty piece of 

 iron-weed ( Vernonia ) five or six feet in diameter nearly all died last 

 year, as a hint that a new place was needed. A little on the spread- 

 ing margin was left alive. 



After growing four years in nearly the same place, a thrifty piece 

 of Euphorbia dentata^ an annual brought from central Indiana, all 

 succumbed to a rust, and Euphorbia nutans is likely to do likewise. I 

 will say that I have lately found a couple of healthy plants of 

 Euphorbia dentata near where the patch was located several years ago, 

 and healthy plants of EupJiorbia nutans can be found in isolated places. 



I have within twenty years seen numerous patches of shepherd's 

 purse become nearly extinct on account of attacks of Cyst opus candi- 

 dus. and patches of knot grass nearly exterminated by rust. In some 

 of these localities a new crop, after a few years, sprang up where the 

 ground had been plowed. 



Where things have gone on in a rather monotonous way for some 

 years, certain insects settle down, live and thrive; meadow mice, 

 moles, squirrels, rabbits, muskrats — all learn the way, and the longer 

 a plant remains in one place in considerable quantity the more it is 

 likely to be disturbed by some of these enemies. As previously ob- 

 served, the same may be said of all sorts of rusts, mildews, microbes 

 and the like. 



In mellow soil, such as the following plants delight in, the root- 

 stocks ( in a few, the roots) run rampant in every direction, encroach- 

 ing on other plants and producing a mixture of species sometimes dif- 

 ficult to untangle. Most of them are the pest of gardeners. Here are 

 some thirty-six of them : 



Agropyron repens, Apios [tuberosa) Apios, Apocynuiii cannabijium, 

 Aristolochia Clematitis, Asclepias Sullivantii, Asclepias Syriaca, Boc- 

 conia cordata, Capriola ( Cynodon ) Dactylon, Carduus ( Cuicus ) arven- 

 sis, Carex riparia, Carex trichocarpa, Convolvulus Scpiuin, Coronilla 

 varia, Cyperus rotundus, Linaria {vulgaris) Linaria, Lyciuui vulgare, 

 Lycopus sinuatus, Lycopus l^irginicus, LysiniacJiia Nununularia, Lysi- 

 machia quadrifolia, Lysimachia {stricta) terrestris, Mentha piperita^ 

 Mentha {viridis) spicata, Onoclea sensibilis, Onoclea Struthiopteris, Poa 



