318 JOURNAL OF THE PLYMOUTH INSTITUTION. 
or dry; is common in bushy waste spots, and sometimes will 
actually arise as a stunted little bush from the crevice of a dry 
wall, as I have seen it doing in the northern part of Plymouth. 
In’ connection with the interdependence of species, I would here 
observe that I have been struck with the wonderful economy in 
the ordering of nature by noticing how many are the creatures 
benefited by only a single large bush of this sallow, or of the 
nearly allied Salix caprea, when covered with catkins in the early 
spring. On it we may see two or three of the glorious peacock 
butterfly (Venessa Io) and as many of the small tortoise-shell 
(V. urtice) that have hibernated through the previous winter, 
several bees of two or three species, and dozens of flies of various 
sorts and sizes, whilst the latter often attract a newly-arrived chiff- 
chaff, which in the pauses of its simple song darts after them 
among the branches, making the whole host to arise from their 
sweet feast in quite a cloud ; then the whole settle again, and con- 
tinue their meal until the little bird has another chase through the 
attractive bush, and once more throws all the busy throng into 
confusion. 
The beech (Fagus sylvatica) possesses in a remarkable degree the 
power of extending itself as a species, through its being able to 
maintain a successful warfare against most other trees, and this 
probably by reason of its greater capacity to grow vigorously in 
crowded situations. We often see it when young pushing its way 
through a dense thicket, and may feel almost certain that ultimately 
its lithe branches will surmount every obstacle, and, moreover, form 
masses so dense as literally to throw all the arboreal vegetation 
around into shade. Think, when a mighty tree of this species is 
felled, what dozens of long-dormant seeds of various species will be 
ready to spring into life through the admission of air and light to 
the ground it covered! and see here another illustration of that 
great fact in nature, the warfare of species. 
Many plants are greatly kept in check by being much sought 
after by certain animals for food. Perhaps the closest grazing 
quadruped we have is the common rabbit, and I have generally 
found turfy spots that it much haunts yield but a small number of 
species, owing probably to very few being able to resist its close 
nibbling. Sheep also on our commons will make turf very bare ; 
and I believe it is they that cause the ling and. heath to appear in 
such well-defined patches as they often do. Probably many of the 
