THE OVULE. 137 



Funiculus. A fully developed ovule is usually attached to the 

 placenta by a short stalk, called the funiculus, podosperm, or umbi- 

 lical cord ; where this stalk does not exist, the ovule is sessile ; in' a 

 few cases the funiculus is very much elongated (Plumbaginaceae). 



Relative Position. Special terms are used to indicate the posi- 

 tion occupied by ovules in the ovary, and more particularly their 

 direction. If the placenta is at the base of the ovary, and the 

 ovule, springing from that situation, points upward, as in Polygo- 

 naceae and Composite, the ovule is called erect ; if it is attached at 

 the summit, and hangs straight down, as in the Birch, Dipsaceae, 

 &c., it is suspended when the placenta is central or parietal, the 

 ovule may turn upwards and be ascending, may point straight out- 

 wards or inwards and be horizontal, or may turn downwards and 

 be pendulous. In Plumbaginaceae the ovule is suspended from the 

 end of a long funiculus, which arises from the base of the ovary as 

 in the erect condition. 



Where numerous ovules exist on a central placenta, it is very common 

 to find the upper ones ascending, the middle horizontal, and the lower 

 pendulous, so that the direction becomes indefinite. 



Parts of an Ovule. The ovule arises from the placenta as a 

 conical papilla, which soon becomes elongated into an oval body, 

 the nucleus, raised on the stalk or funiculus. By the time the 

 flower opens, the nucleus (figs. 268270, a) generally becomes 

 covered up by the coats or envelopes, which originate as circular ridges 

 from the point where the funiculus is attached, and gradually grow 

 up over the nucleus. The coats do not completely close in the 

 ovule, but leave an opening at its summit, called the micropyle or 

 foramen (figs. 268-270, ft). The base of the nucleus, where the 

 coats arise, is called the clialaza ; the internal coat (the secundine 

 of Mirbel) is the first formed ; it is denominated the integumentum 

 internum, or the tegmen ; where only one coat exists, it is called the 

 integumentum simplex. The outer coat, which grows up after the 

 inner (the primine of Mirbel), is called the integumentum eocternum, 

 or sometimes the testa. Sometimes, as in Welwitscliia, the primine 

 is prolonged beyond the apex of the .ovule in the form of a tube 

 greatly resembling a style (see under Grnetaceae). The orifice named 

 the micropyle forms a canal passing through both coats down to the 

 point of the nucleus ; and the portions passing through the outer and 

 inner integuments are often called, respectively, the exostome and 

 endostome. The point where the seed afterwards breaks away from 

 the f uuiculus is marked by a scar, which is called the hilum. 



In the Mistletoe the nucleus is naked, no coats being formed ; in many 

 cases there is only one coat ; most ovules of Monocotyledons have two. 



