GYNCEC1UM IN ANGIOSPERMS. 259 



unaltered until it is placed upon the stigma. The more or less 

 viscid moisture of this incites a sim- 

 ilar growth, and also doubtless nour- 

 ishes it ; and the protruding tube at 

 once penetrates the stigma, and by glid- 

 ing between its loose cells buries itself 

 in the tissue of the style, descending 

 thence to the interior of the ovary and 

 at length to the ovules. Fertilization 

 is accomplished by the action of this 

 pollen-tube upon the ovule, and upon a 

 special formation within it. Consequent 

 upon this an embryo is formed ; and the ovule now becomes a seed. 



SECTION VII. THE PISTILS, OR GYNCECIUM. 



1. IN ANGIOSPERMS. 



476. The succinct description of the pistil in the first section 

 of this chapter (302), as also what has been stated of the modi- 

 fications of the gyncecium in Section III., relates to the most 

 typical conditions of this part of the flower. The essential 

 characteristics of all ordinary pistils, whether simple or compound, 

 are : 1. a closed ovary, in which one or more ovules are included ; 

 and 2. a stigma, upon which pollen for fertilizing the ovules is 

 received, and through which the pollen acts upon them. There 

 is a more simplified condition, in Gymnosperms, in which naked 

 ovules are exposed to the direct action of the pollen. In con- 

 tradistinction to this, the ordinary pistil is said to be Angiosper- 

 mous ; that is, with the seeds enclosed in a sac or covering, this 

 in the flower being the ovary. 1 And plants with such g3'no2cium 

 are denominated ANGIOSPERMS or ANGTOSPERMOUS PLANTS. To 

 such only the present subsection specifically relates. 



477. The several terms which apply to the Gyncecium or 

 female system of a flower, and to its components, have been 



1 Although thus originated, the seeds are not in all cases matured in a 

 closed pistil. In the Blue Cohosh, Caulophyllum thalictroides, the ovules 

 rupture the ovary soon after flowering, and the seeds become naked ; and in 

 Mignonette they are imperfectly enclosed, the ovary being open at the 

 summit from an early period of fructification. 



FIG. 523. A pollen-grain of Datura Stramonium, emitting its tube. 524. Pollen- 

 grain of a Convolvulus, with its tube. 525. Other poll en -grains, with their tubes, less 

 strongly magnified. 526. A pollen-grain of the Evening Primrose, renting on a portion 

 of the stigma, into which the tube emitted from one of the angles penetrates; the oppo- 

 site angle also emitting a pollen-tube. All highly magnified. 



