THE DISPERSION OF SEEDS AND SPOKES. 51 



by which dispersion is effected in the case of 

 flowerless plants. These, it is true, are not propa- 

 gated by seeds, but by spores. The nature of the 

 body to be dispersed is, however, of secondary 

 importance, and the functions of seeds and spores 

 are so much alike that we may, for the present, 

 neglect this distinction. Indeed, one feels very much, 

 in pursuing such an investigation as the present, 

 how desirable it would be to get rid of the terms 

 "flowering" and "flowerless" altogether. It would 

 certainly conduce to clearness if we could discard 

 entirely the artificial distinction between Phanerogams 

 and Crj^ptogams. The distinction disappears when 

 we remember that a flowering plant may be regarded 

 as simply one of the higher Cryptogams producing 

 like Selaginella two kinds of spores — the pollen-grain 

 corresponding to the microspore, and the embryo- 

 sac to the macrospore. 



We are familiar with many contrivances for 

 securing the distribution of pollen-grains in order 

 to cross-fertilisation. These present so close an 

 analogy to the provisions for the dispersion of 

 seeds, that it is well to consider both together. We 

 have therefore here to concern ourselves with 

 distribution in the widest sense. The bodies dis- 

 persed may differ in structure and morphological 

 value, but the means of transport are very much 

 the same. The body dispersed may be as follows : 



1. The entire plant : Protococcus, Bacteria, etc. 



2. A bud or branch : Marchantia, Swan's-neck moss. 



3. A vegetative cell : spores of ferns, fungi, etc. 



4. The sperm or male sexual cell : antherozoids, 

 microspores, pollen-grains. 



5. The germ or female cell : macrospores of 

 Selaginella, Isoetes, etc. 



6. The fertilised germ or embryo : exalbuminous 

 seeds. 



A seed is simply an embryo invested by a portion 

 of the mother plant. In this covering three layers 

 may usually be distinguished : the nucleus, the 



