THE STEUCTUKE OF PLANTS. 



13 



The terms upper and lower, as applied to the parts of the flower, refer 

 to their position in relation to the main stem or axis. The petal or 

 sepal of an axillary flower, which lies next to the bract or farthest out- 

 ward from the stem, is lower or anterior ; the one on the opposite side 

 and nearest the stem is upper or superior ; and those placed right and 

 left of these are lateral. 



45. The Pistil in its simplest form, a single pistil, is regarded as a 

 leaf with its margins folded together so as to form a closed bag or hol- 

 low portion, the ovary ; its prolonged apex is the style, and the uj)per 

 end of this or some portion of its margin, the stigma, A simple pistil, 

 composed of a single leaf, whether separate or forming a part of a com- 

 pound pistil, is called a Carpel; that portion where the margins of the 

 leaves join, is the Ventral Suture ; and the portion opposite to this cor- 

 responding to the midrib of the leaf, the Dorsal Suture. The Ovules 

 (37) are placed at the ventral suture where the margins of the 

 carpellary leaf are infolded and project more or less into the cavity, 

 forming what is called the Placenta, to which the ovules are attached. 



46. When two or more carpels unite, a Compound Pistil is formed ; 

 this will have as many cells or cavities as there are simple pistils or 

 carpels combined ; the placenta will be in the centre and the partitions or 

 Dissepiments Avhich separate the cells, being formed by the union of the 

 contiguous sides of two carpels, will' be double in ilieir nature, although 

 this may not be manifest (Fig. 33 represents a compound pistil of 3 

 carpels, cut across). Sometimes a compound pistil is but one-celled ; 

 either from the early disappearance of the partitions, when the placen- 

 tse will be left free in the centre of the ovary ; or the ovary may be 

 formed by the union of the contiguous edges of several carpellary leaves, 

 without their folding together, — the placentae in this case consist of the 

 margins of two different leaves and may not project into the cavity of 

 the ovary — such placenta are parietal, (i. e., on the walls). The num- 

 ber of carpels of which a compound ovary is composed, is frequently in- 

 dicated by the number of styles or stigmas. An ovary of two carpels is 

 dtcarpellary ; one of three, tricarpellary, &c. 



47. The ovules are the little rudimentary bodies which are to become 

 seeds : our limits do not permit us to describe their structure or to say 

 much about them. After they have received the fertilizing influence of 

 the pollen, communicated through the stigma, an embryo is developed 

 within them as they mature, and a seed is formed. Each ovule is placed 

 on a little stalk, the Funiculus. When the ovule is straight it is called 

 orthctropous ; when curved or bent upon itself, campy 'otropous ; and if 

 entirely inverted on its stalk so that its apex points to the placenta, 

 anatropous. 



48. Not only does the ovule enlarge and undergo a great change, in 

 forming the seed, but the ovary also enlarges and is variously trans- 

 formed and becomes the fruit. The Fruit is the ripened ovary, (called 

 Pericarp or Seed-vesse' ,) its contents and sometimes the adhering adjacent 

 parts, as the calyx. In the Checkerberry (Fig. 147) and in the Quince, 

 it is the enlarged and fleshy calyx which is the eatable portion of the 



