58 MR. C, BAILEY ON THE STllUCTURE ETC. 



must surely prove potent factors in transporting pollen not 

 only in the tepid water of the Reddish canal^ but in the 

 still water of pools and ditches. If we carefully look for 

 instances of their intervention we cannot fail to find 

 distinctive protozophilous plants^ dependent for their fer- 

 tilization upon animal life in the aqueous world^ in much 

 the same way as we find entomophilous plants in the 

 aerial world. 



It is a very happy circumstance that Sir Joseph Hooker 

 should have indicated, in the new edition of his ' Student^s 

 Flora ^ recently published, the forms of pollination which 

 prevail in many of our native plants, where known. 

 Sprengel, Darwin, Miiller, Lubbock, Kerner, and many 

 others have largely increased our knowledge of this sub- 

 ject for terrestrial plants, but its extent after all is very 

 limited ; we have but ascended a few steps leading up to 

 the vestibule, whilst the great temple of truth is beyond; 

 while, as regards aquatic plants, and particularly those 

 which are wholly submersed throughout their lives, like 

 Naias graminea, Str-atiotes, &c., our knowledge is even 

 more limited. Hence Sir Joseph Hooker has earned the 

 thanks of British botanists by bringing into prominence 

 this important feature in the economy of our native 



plants. 



XIV. The Fruit. 



Up to the time of the fertilization of the ovule the outer 

 membrane of the flower — the perianth — and the investing 

 membrane of the ovule contained within the perianth, both 

 remain transparent or semitransparent. After pollination 

 has taken place the membrane of the ovule becomes turbid 

 and thickens, while the ovule itself enlarges and becomes a 

 mature fruit, covered with a testa formed of thick- walled 

 cells (figs. 81-83). 



The fruit is sculptured with a network of raised ridges, 



