HOW PLANTS FLEE FROM THEIR ENEMIES. 



SOME REASONS FOR PLANT MIGRATIONS. 

 By W. J. Beal. 



W 



(CONCLUDED.) 



ERE permit me to quote a little from a paper presented at the 

 recent meeting of the Society for the promotion of Agricultu- 

 ral Science : 



" It is very instructive to note how much better many of the weeds thrive 

 when they get away Irom the spots where they have been confined for two to six years. 

 Seedlings ot Datura Tatula are larger in the bed of PUmtago major than they are 

 in their own bed where their parents grew. After three years the plantain men- 

 tioned has nearly run out, and Aniaranthus albiis has entirely disappeared. Che- 

 nopodiimi album grew finely for a couple of years, but of late has made a small dis- 

 play, and has suffered from the attacks of insects and probably from other causes. 



Panicum Crus-galli behaved like Chenopodium, and has had a hard time 

 of it. needing considerable attention. Barnyard grass likes the best that can be 

 got, and if it can't get that, will go into a rapid decline. 



The seedlings of Polygonum Persicaria are feeble this year and are over- 

 topped by intruders from adjoining plots, such as ragweed and prickly lettuce. 



ChowpoduDii glaucum doesn't seem very persistent for a plant that ranks 

 among the weeds, but it shies off from its home ground as though searching for 

 fresh fields. Phlaspi arvense is very feeble, and like the last, seems to be hunting 

 for a soft place that just suits it. Polyg07iuni avtculare grows near the foot- path 

 about the doors of dwellings, and thrives with abuse, seeming to enjoy tramping 

 upon by feet, but in my plots, I have difficulty in growing it. Insects prey upon 

 it; rust causes it to dwindle and disappear. Motherwort grows rank, four feet high 

 near the barnyard fence and the flowers are covered with bees, but when kept several 

 years in the same bed it goes off into the sulks as though neglected. In moist, rich 

 and mellow siol Cyperus escult'?ilus grows luxuriantly for a couple of years, and 

 after that makes little display, as though tired out and pining for something new." 



Almost every one has seen or heard about fairy rings often seen in 

 lawns or old pastures. Here some species of fungi, such as Marasmius 

 orcoidcs and others spread out a foot or so each year, more or less, 

 in the form of a circle, killing or weakening the grass where it grows. 

 These plants seem to require a fresh place for growth each year. 



Marsilia qtiadrifolia and the wild rice {Zizania aquatica) have 

 often been driven from the pond to the extreme margin and sometimes 

 above the edge of the water by some insect, crustacean or snail. Be- 

 yond the reach of these enemies they thrive well from year to year. 

 During the wanter of 1894-95 the ice on the pond was solid and of un- 

 usual thickness for many weeks. The loss of air, with the cold or some- 

 thing else caused the death of all the fish and most likely many of the 

 other small animals. The following suminer Marsilia and wild rice 

 spread out and grew in the water as never before nor since, for their 

 enemies had been killed. Pringle, in notes on Mexico, speaks of col- 

 lecting grasses beneath the thorn bushes, where they had not been 

 reached by cattle. 



