106 THE FLOWERING PLANT. 



primrose will show that there is a single cavity into which a 

 knob-like placenta projects, upon which numerous ovules are 

 situated. This kind of placentation is free central. The presence 

 of tw r o styles points to two carpels, but in primrose the pistil is 

 from the first absolutely devoid of branching or lobation. Is it 

 then a single carpel ? If so, it would naturally have a ventral 

 suture, and be bilaterally symmetrical, as is the case in the pea. 

 But the pistil of primrose is absolutely terminal and radially 

 symmetrical ; and in thrift, a plant belonging to a closely related 

 family, the flowers agree very nearly with those of primrose, 

 excepting only that live styles are present. A great deal of 

 discussion has arisen as to the nature of the knob- like placenta 

 in the primrose and other forms. Some regard it as the dilated 

 end of the axis. If so, the placentation is axial, i.e., the ovules 

 are borne by the axis, and not by the carpels. (N.B. — Do not 

 confound this term with axile.) But the knob may very possibly 

 be more or less formed from the carpels. It is best, for the 

 present, to keep the word free-central, as that simply refers to 

 the way of arrangement. There are other cases in which the 

 ovules are, or appear to be, developed on the axis. In docks, for 

 instance, a single ovule grows straight up from the bottom of the 

 unilocular ovary, apparently forming the end of the axis. The 

 florets of daisy, dandelion, sunflower, &c, present a seed-like 

 structure beneath the coloured corolla. This is the inferior ovary. 

 Although there are two cohering carpels, as shown (fig. 44) by 

 the forked style (cf. p. 100), the ovary contains but one cavity, 

 from the base of which a single ovule rises. Just by the side of 

 it is a minute knob. This represents the end of the axis, upon 

 the side of which the ovule appears to be borne. 



An ovule may take various directions. When growing up 

 from the bottom of a loculus, it is erect, as in dock. An ovule 

 developed on the side of a loculus is very frequently horizontal, as 

 in lily. Advantage is taken of this fact in procuring longitudinal 

 sections of the ovules, i.e., transverse sections of the ovary are 

 made. Or such an ovule maybe directed upwards, ascending, e.g., 

 buttercup, or hanging downwards, 2?endidous, as in rose. If it 

 hangs down from the top of the loculus, it is suspended. Anemone 

 is an instance. When one or a few ovules only are present, more 

 attention is paid to their direction than when a large number exist. 



Nectaries may be situated on the pistil. The best example of 

 this is found in inferior ovaries, upon the top of which a fleshy 

 honey-secreting cushion, commonly called the disc, is often pre- 

 sent. Parsnip, hemlock, and daisy are good examples. The 

 nectary of dead nettle is a fleshy outgrowth from the front of the 

 ovary. 



