THE DISPERSION OF SEEDS AND SPORES. 73 



office be taken to represent the primary centre of 

 dispersion, the branch offices will correspond to the 

 secondary. The delivery of any extra large mass of 

 correspondence, such as that with which the postal 

 authorities have to contend at Christmas, presents 

 nearly the same problems as the distribution of 

 plant-germs. The delivery of the letters may be 

 effected directly from the head office ; but a smaller 

 number of men would suffice were all the letters for 

 each district in the city despatched to the various 

 branch offices, and the letter-carriers then to proceed 

 with the delivery from these new centres. The 

 delivery, too, would be greatly facilitated if every 

 house in the city were provided with a letter-box. 

 Applying now our illustration, we may compare the 

 Conifers to a city in which all the work is accomplished 

 from the central office, there being no branch offices 

 and a complete absence of letter-boxes. In wind- 

 fertilised Phanerogams, the delivery is made from 

 the general post-office, while the fringed and feathery 

 stigmas play the part of letter-boxes. The higher 

 Cryptogams, again, correspond to a city in which 

 the delivery is effected from secondary centres, 

 and in which a mode of conveyance is employed to 

 carry the letter-bags from the general to the branch 

 offices different from that used to take the letters 

 from the branch offices to the houses. The micro- 

 spores correspond exactly to the mail-bags distributed 

 to the branch offices, and the antherozoids to the 

 letters they contain. To complete the analogy, we 

 should have to imagine a city in which the mail- 

 bags were carried from the general to the branch 

 offices by balloon, and that from the district offices 

 the letters themselves marched out in all directions 

 to their respective destinations, where, in the absence 

 of letter-boxes, they pushed themselves under the 

 doors. 



(6) Seeds. — The seeds of Phanerogams are of larger 

 size and fewer number, and require more obvious 

 adaptations, than pollen grains or spores. Neverthe- 



