2!! Tin- ri<n-<i <>/'(/ Cftmbn'(/t/r 



This list could probably be greatly expanded; as it stands 

 it is too small to generalise from. It is worth noting however 

 that two, Minwitix colliiHi and rcrxinilur, are peculiarly fitted 

 for animal distribution. 



As the earth gets older, the annuals are replaced by 

 perennials, but of a different sort from those of the surround- 

 ing vegetation. Sedum acre and Centatimn arvense, especially 

 the former, abound. These seem to hold their Around well, 

 particularly if the soil is loose and very dry, as is the 

 upon the hillocks which are so often chosen by the rabbits for 

 their holes. 



Here on this heath we have almost a primitive state of 

 vegetation; man plays so small a part in the economy of 

 nature that he can almost be neglected. Here we find certain 

 species occupying great areas of country, undisturbed and 

 unchecked by any agricultural operations. 



Annuals are rare plants, what w r e now call corn-field 

 annuals exceedingly rare. These depend for their very exist- 

 ence upon the constant and regular disturbance of the soil. 

 Originally such plants, in those portions of the world where 

 they had not invaded the cultivated land of primitive man, 

 must have led a precarious existence upon land-slips, bare 

 and crumbling river banks, but principally upon the earths of 

 burrowing animals. 



It is on the rabbit earths and on these alone that, in the 

 wilder portions, annuals can exist. "We see to-day the rabbit 

 performing, in this quiet corner of England, his ancient ro/<- "f 

 agriculturist. 



3. The Meadows. 



The meadow association, which is marked on the map grey 

 blue, occupies the river valleys of some of the streams round 

 Cambridge. It is seen at its best where the rivers have cut 

 through the chalk to the gault, and formed a flat valley 

 bordered by low hills, which are for the most part cultivated. 



These damp valley meadows are in such marked contrast 



