310 



THE FLOWER. 



mil of the ovary and hang perpendicularly in the cavity (Fig. 316). 

 In the Thrift (Ord. Plurnbaginacea?), and in the Sumach, the ovule 

 is singularly pendent from an ascending funiculus. These terms 

 are applicable to the seed as well as to the ovule. 



563. As to its structure and formation, the ovule appears as a 

 mere excrescence, or papilla, of soft and homogeneous parenchyma, 

 which soon acquires a definite form. This NUCLEUS, as it is called, 

 is the essential part of the organ ; in the Mistletoe it actually con- 

 stitutes the whole, its ovule having no integuments of its own. A 

 hollow place is formed in its interior about the time of flowering, 

 in which the embryo at length appears. Most ovules, however, in 

 the course of their growth acquire an envelope, or more commonly 

 two envelopes. Only one envelope is seen in the ovule of the Wal- 

 nut, where, after the nucleus is formed and has assumed its ovate 

 shape, a circular ring appears around its base, which gradually 

 enlarges into a sheath, but at length covers it like a sac, which, 

 however, remains open at the apex. This orifice, which leads to 

 the nucleus, and through which, indeed, the nucleus often pro- 

 trudes, is called the FORAMEN or the MICROPYLE. In far the 

 greater number of cases, a second envelope is formed outside of 

 the first, beginning in the same way, though always later than the 

 inner one, which, however, it eventually overtakes and incloses. 

 The outer envelope, when both are present, becomes the exterior 



integument or testa of the 

 seed ; and the inner, its teg- 

 men or inner coat. Mirbel 

 named the exterior coat of the 

 ovule the PRIMINE, and the in- 

 terior the SECUNDINE,, names 

 which are attended with the 

 objection that the secundine or 

 second coat is actually older 

 than the primine or first coat 

 in the order of position. Both 

 sacs are open at the apex, and the summit of the nucleus points 



412 



FIG. 410. An orthotropous ovule. 411. Longitudinal section of the same, more magnified: 

 a, the primine ; b, the secundine ; c, the nucleus ; d, the chalaza. 412. An amphitropoua 

 ovule. 413. Three anatropous ovules, with their funiculi, attached to a portion of the placenta. 

 414. One of the same, more highly magnified, exhibiting its cellular structure. 415. A campy- 

 lotropous ovule. 



