OF PLANTS. 
199 
and prickles; in mushrooms, placed under a penthouse; in 
ferns, within slits in the back part of the leaf; or (which is 
the most general organization of all) we find them covered 
by strong, close tuniclesp and attached to the stem accord¬ 
ing to an order appropriated to each plant, as is seen in 
the several kinds of grain, and of grasses. 
In which enumeration, what we have first to notice is, 
unity of purpose under variety of expedients. Nothing 
can be more single than the design; more diversified than 
the means. Pellicles, shells, pulps, pods, husks, skin, 
scales, armed with thorns, are all employed in prosecuting 
the same intention. Secondly; we may observe, that, in 
all these cases, the purpose is fulfilled within a just and 
limited degree. We can perceive, that if the seeds of plants 
were more strongly guarded than they are, their greater 
security would interfere with other uses. Many species 
of animals would suffer, and many perish, if they could 
not obtain access to them. The plant would overrun the 
soil; or the seed be wasted for want of room to sow itself. 
It is sometimes as necessary to destroy particular species 
of plants, as .it is at other times to encourage their growth. 
Here, as in many cases, a balance is to be maintained be¬ 
tween opposite uses. The provisions for the preservation 
of seeds appear to be directed, chiefly, against the incon¬ 
stancy of the elements, or the sweeping destruction of 
inclement seasons. The depredation of animals, and the 
injuries of accidental violence, are allowed for in the abun¬ 
dance of the increase. The result is, that out of the many 
thousand different plants which cover the earth, not a sin¬ 
gle species, perhaps, has been lost since the creation. 
When nature has perfected her seeds, her next care is 
to disperse them. The seed cannot answer its purpose 
while it remains confined in the capsule. After the seeds 
therefore are ripened, the pericarpium opens to let them 
out: and the opening is not like an accidental bursting, 
but, for the most part, is according to a certain rule in each 
plant. What I have always thought very extraordinary; 
nuts and shells, which we can hardly crack with our teeth, 
divide and make way for the little tender sprout which pro¬ 
ceeds from the kernel. Handling the nut, I could hardly 
conceive how the plantule was ever to get out of it. There 
are cases, it is said, in which the seed-vessel, by an elastic 
jerk at the moment of its explosion, casts the seed to a 
distance. We all however know, that many seeds (those 
of the most composite flowers, as of the thistle, dandelion, 
&c.) are endowed with what are not improperly called wings , 
