THE SIMPLE PISTIL. 



289 



of the altered leaf turned outwards, either at the tip or along the 

 inner side of the style, form the stigma. This will be clearly un- 

 derstood on comparing Fig. 342 and Fig. 491, which are pistils 

 transversely divided, with Fig. 490, a leaf curved inwards until its 

 margins nearly meet, and with Fig. 

 492, a simple pistil of Caltha or 

 Marsh-Marigold which has matured, 

 split open along the inner side to 

 discharge the seeds it bore, and 

 spread out into the shape of a leaf. 



543. The line formed by the union 

 of the margins of the leaf is called 

 the Inner or Ventral Suture, and 

 always looks towards the axis of the 

 flower. This is a true suture, or 



seam, as the word denotes. The opposite line, answering to the mid- 

 rib, is sometimes apparent as a thickened hne, and is termed the 

 Outer or Dorsal Suture. The ovules or young seeds are borne (in 

 all ordinary cases at least) on the inner sutu^, or some part of it ; 

 that is, on what answers to the united margjns of the infolded and 

 transformed leaf. The part in the cell of the ovary to which the 

 ovules are attached, and which is commonly more or less enlarged 

 or projecting when the ovules are numerous, is named 



544. The Placenta. As this corresponds with the ventral suture, 

 and is in fact a part of it, or a cellular growth from it, it always 



belongs next the axis of the flower ; 

 as is evidently the case when two, 

 three, or more pistils are present. 

 Each placenta necessarily consists of 

 two parts, one belonging to each margin 

 of the transformed leaf. It therefore is 

 frequently two-lobed, or of two diverg- 

 ing lamellae (Fig. 342). This shows 

 why the ovules are apt to occupy two longitudinal rows, as in 



FIG. 490. A leaf infolded, to illustrate the theory of the formation of the pistil. 



riG. 491. Pistil of Isopyrum biteroatum, cut across ; the inner or OTule-bearing side 

 turned towards the observer. 



FIG. 492. Eipe pistil of Caltha palustris, after opening and discharging the seeds. 



FIG. 493. Vertical section of a pistil of Schizandra coccinea; a side view. 494. Pistil of 

 Hydrastis. 496. Pistil of Act%a rubra, cat across, so as to show the interior of the ovary (the 

 ventral suture turned towards the observer). 



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