THE ORIGIN OF FRUITS. 603 



Doubtless the earliest seeds differed but little from the spores of 

 ferns and other flowerless plants in the amount of nutriment with which 

 they were provided and the mode in which they were dropped upon the 

 nursing soil beneath. But as time went on, during the great secondary 

 and tertiary ages of geology, throughout whose long course first the 

 conifers and then the true flowering plants slowly superseded the gi- 

 gantic horsetails and tree-ferns of the coal-measures, many new devices 

 for the dispersion and nutrition of seeds were gradually developed by 

 the pressure of natural selection. 1 Those plants which merely cast 

 their naked embryos adrift upon the world to shift for themselves in 

 the fierce struggle of stout and hardy competitors must necessarily 

 waste their energies in the production of an immense number of seeds. 

 In fact, calculations have been made which show that a single scarlet 

 corn-poppy produces in one year no less than 50,000 embryos ; and 

 some other species actually exceed this enormous figure. If, then, any 

 plant happens by a favorable combination of circumstances to modify 

 the shape of its seed in such a manner that it can be more readily con- 

 veyed to open or unoccupied spots, it will be able in future to econo- 

 mize its strength, and thus to give both itself and its offspring a better 

 chance in the struggle for life. There are many ways in which natural 

 selection has effected this desirable consummation. 



The thistle, the dandelion, and the cotton-bush, provide their seeds 

 with long tufts of light hair, thin and airy as gossamer, by which they 

 are carried on the wings of the wind to bare spaces, away from the 

 shadow of their mother-plant, where they may root themselves success- 

 fully in the vacant soil. The maple, the ash, and the pine, supply their 

 embryos with flattened wings, which serve them in like manner not less 

 effectually. Both these we may classify as wind-dispersed seeds. A 

 second set of plants have seed-vessels which burst open explosively 

 when ripe, and scatter their contents to a considerable distance. The 

 balsam forms the commonest example in our European gardens ; but a 

 well-known tropical tree, the sand-box, displays the same peculiarity in 

 a form which is almost alarming, as its large, hard, dry capsules fly 

 apart with the report of a small pistol, and drive out the disk-shaped 

 nuts within so forcibly as to make a blow on the cheek decidedly un- 

 pleasant. These we may designate as self-dispersed seeds. Yet a third 

 class may be conveniently described as animal-dispersed, divisible once 

 more into two sub-classes, the involuntarily and the voluntarily aided. 

 Of the former kind we have examples in those seeds which, like burs 

 and cleavers, are covered with little hooks, by whose assistance they 

 attach themselves to the fur or wool of passers-by. The latter or vol- 

 untarily aided sort are exemplified in fruits proper, the subject of our 



1 1 trust that in the sequel the critical botanist will excuse me for having neglected 

 the strict terminology of carpological science, and made no distinction between seeds and 

 fruits. Some little simplification is absolutely necessary for general readers in this the 

 most involved department of structural botany. 



