136 GENERATION. 



227. The diffusion of the pollen upon the surface of 

 the stigma takes place most quickly after the dehiscence 

 of the anther, of course in those cases in which the 

 flowers are Hermaphrodite, and the anthers placed near 

 to or on a level with the stigma ; on the other hand, when 

 the plant is Monaecious or Disecious, and even in Her- 

 maphrodite flowers, when the position of the sexual 

 organs is not as we before stated, a more or less 

 lengthened period must ensue ; and not only this, but 

 often some intermediate means, independent of the 

 plant, must exist, by which it may be effected. 



228. These are generally insects and wind, the former 

 flying about from flower to flower in search of nourish- 

 ment, and attracted by the saccharine matter found in 

 many floral structures, in their endeavours to obtain it 

 rub their bodies against the anther, and thus carry off 

 with them in their flight the pollen, which by their after- 

 wards alighting upon a female flower is enabled to fulfil 

 its purpose. The wind disperses pollen in the air, which 

 at length falls upon different objects, and amongst them 

 the female flowers of plants ; the Sulphur rain, as it is 

 termed, being nothing more or less than quantities of 

 the pollen of Pinus sylvestris, cairied about in the air 

 and afteward deposited. 



229. In many plants the stamen, at the time the 

 anther bursts, and the pollen should be evacuated, moves 

 toward the stigma. In other cases the stigma moves to 

 the stamen, and again both may approach toward each other, 

 in order that the necessary contact may be effected. 

 All such cases afford examples of irritability. 



230. The pollen being fixed upon the stigma, the 

 next thing that takes place is the protrusion of the pollen- 

 tube. In general only one tube protrudes from each 

 grain of pollen, though in some cases, it is said, that 

 several may be seen ; as the protrusion of the tube goes 

 on, it pierces through the stigma, and proceeds down- 

 wards to the ovarium through the interior of the style ; 

 as it runs down the style, its course is mostly pretty 



