184 The Great World's Farm 



when it is ready. If it does, the sheath is gradually filled 

 with water, and the pollen is floated up till it reaches the 

 right place. 



There is a still more curious arrangement in the case 

 of the Vallisneria, which grows in the ditches in Italy, and 

 is well known, though not in a flowering state, in fresh- 

 water aquariums. This plant bears its pistillate and stami- 

 nate blossoms on separate roots, which, however, seem to 

 grow near one another. The pistillate, fruit-bearing blos- 

 som grows on a long, slender stalk twisted like a cork- 

 screw, which uncurls and raises the bud just above the 

 surface of the water when it is about to open. The 

 barren, staminate, or pollen-bearing flowers, grow in great 

 numbers on short, upright stalks under water; but just 

 about the time when the other blossoms up above open 

 and want their help, these buds loose themselves from 

 their stalks and rise up like little air-bubbles, opening sud- 

 denly when they reach the surface. Here they float about 

 on the water among the pistillate blossoms in such num- 

 bers that they often quite cover them, and by this means 

 convey to them the necessary pollen. When this has been 

 received, the corkscrew stalks, which are often as much 

 as ten feet long, curl up as before, and the fertilized blos- 

 soms sink down again to ripen their fruit under water. 



We must now, however, turn to the insects, among 

 which bees have a foremost claim upon our attention, 

 since none are more generally useful in carrying on the 

 very important work of fertilization. Creeping insects are 

 not, as a rule, useful visitors for flowers, as any grains of 

 pollen which they may pick up by the way are liable to be 

 brushed off again before they reach a blossom which might 

 be benefited. But flying insects of all kinds, even to the 



