SOME PLANT MARRIAGES 



449 



and water, which, having no senses to be appealed to, would be unaffected 

 by colour, sweets, or scent. Yet being wasteful carriers, these agents 

 require abundance of pollen ; and, if water is to be the vehicle of trans- 

 mission, the pollen must be either lighter than the water or of like specific 

 gravity : if wind be the agent, the pollen must be smooth, light, and 

 incoherent. In the vast majority of cases these conditions are found to 

 be wonderfully fulfilled. 



Of hydrophilous plants some are adapted for fertilization under the 

 water: and these 

 are provided with a 

 pollen of like speci- 

 fic gravity to the 

 surrounding fluid ; 

 others are adapted 

 for fertilization at 

 the surface, and the 

 pollen of these 

 unless borne upon 

 a floating raft is 

 specifically lighter 

 than the water. 

 The Grass-wracks 

 (Zoster a] are re- 

 markable for pro- 

 ducing a pollen the 

 grains of which do 

 not, like the- gener- 

 ality of pollen- 

 grains, burst in 

 water. Moreover. 

 the grains assume 

 the form of elon- 

 gated cylindrical 

 tubes on quitting 

 the anthers, which 



greatly facilitates their conveyance through the water to the threadlike 

 stigma of the flowers. Something almost analogous takes place in certain 

 cryptogamic plants notably the Floridece or Red Seaweeds where the 

 male cells are neither motile nor provided with hairs, but are borne about 

 passively by currents of water till they attach themselves to the slender 

 projecting terminal cells of the female organs. 



The Sea Ruppia or Tassel-grass (R. maritima), closely allied to Zostera, 

 is a widely distributed plant adapted for pollination on the surface of water. 

 At the period of maturity the submerged flower-stalk lengthens, and the 

 iill 



Photo by] 



[E. Step. 



FIG. 553. SCOTS PINK (Pinus sylvestris). 



The male flowers [are here shown spirally arranged in spikes and a large number of 

 spikes forming a cluster. Tne female (lowers are borne on the same tree, but on 

 separate branches. 



