ON THE DISPERSAL OF SEEDS BY MAMMALS. 25 



seeds in holes as the English squirrel does for the winter. 

 Among the oaks, which are more abundant than the chest- 

 nuts, there seems at first sight even less protection for the 

 seed or means for its dispersal than for the latter, but there 

 are certain slight modifications which have a most important 

 effect in these matters. The acorn is nearly always quite 

 exposed, and the cup, which corresponds to the involucre of 

 the chestnut, is not armed, although in some species it is 

 roughened with soft hooks {Quercus Jiystrix). 



If one examines the acorns which have fallen from a tree 

 where there are many squirrels, one notices that they are all 

 nibbled at the base, and there are often marks of teeth as of 

 ineffectual bites on the sides. I gave a Sciurus bicolor some 

 acorns of Quercus liicida, a large rounded acorn with a thick 

 but shallow cup. Taking them between its paws, it made an 

 attempt to bite into the side of the acorn, but the outer coat 

 was so smooth that its teeth slipped and it could not get a 

 hold. It then turned the acorn round and bit the cup, and 

 the acorn immediately fell out of the cup and rolled away. 

 Had it been up in a tree when it tried to eat the acorn, 

 the fruit would have fallen down and rolled perhaps far from 

 the parent tree. On giving it the acorn again it began to bite 

 the rim at its base, but it was clear that the smooth polished 

 surface of the fruit was too slippery for its paws, and even on 

 the floor of its cage it had some trouble in holding it. 



Many of the acorns have a fairly firm outer coat thus 

 polished, and fall very readily from the cup when ripe, but 

 some such as Q. encleisocarpa, and Q. Cant ley iy two of 

 our commonest species, have an improvement on this. The 

 acorn is coated with a very fine silk, which has almost a 

 greasy feel. It is not at all easy for a squirrel to hold these in 

 its paws to eat, and it is very common to see the acorns of the 

 former scattered all over a wood in which there is a tree in 

 fruit, and nearly all of these bear the marks of squirrels' teeth, 

 but for all practical purposes are unhurt, Q. encleisocarpa 

 has the cup in the form of a thin brown covering, from which, 

 though it is much cracked and split when ripe, the acorn 

 never falls. In Q. Cantieyi the acorn is readily detached 



