OVULE. 



83 



cellular substance, nearly transparent, with its base forming a 

 part of the wall of the ovary. If we examine a bud a little 

 later, we shall find a ring swelling out from the base of the 

 nucleus, expanding and rising round it, and forming a partial 

 covering to it. (Fig. 136, 2, a.) This first integument is 



n, the nucleus ; a, the secundine ; b, the primine ; /, the funiculus ; h, the hilum. 



Fig. 137 



called the secundine by Mirbel, and is scarcely formed when a 

 second makes its appearance in the same manner, which is 

 called the primine, and both increase until they present the ap- 

 pearance represented in Fig. 136, 3, in which n represents the 

 nucleus, a the secundine, or internal membrane of Brown, the 

 inner envelope, and b the primine, or external membrane of 

 Brown, which is the outer one. These continue to increase 

 until they inclose the nucleus entirely, leaving only a micro- 

 scopic orifice, called the foramen, in the ovule, and micropyle in 

 the seed. 



137. This is the mode of development 

 of all ovules that have integuments around 

 the nucleus. The ovule is attached to 

 the ovary by a bundle of vessels, of greater 

 or less length, which is called the funicu- 

 lus. (Fig. 136, 1,/.) The point of at- 

 tachment to the ovule is called the hi- 

 lum. (Fig. 136, 2, h.) The hilum is 

 always the base, and the foramen the 

 apex of the ovule. 



138. When the parts are developed 

 as above described, that is, when the nu- 

 cleus remains in its original position, with 

 its base next the placenta, and its apex in the opposite direc- 

 tion, the ovule is said to be orthotropous (orthos, straight, 



r, the raphe. 

 cA, the chalaza 

 o, foramen. 

 n, nucleus. 



a, secundine. 



b, primine. 

 /, funiculus. 

 h. hilum. 



What do we find later ? What did Mirbel call it? What next makes 

 its appearance ? What is it called ? What is the foramen ? What is it 

 called in the seed ?— 137. How is the ovule attached ? What is it called? 

 What is the Hilum ? What is the base of the ovule ? What is the apex ? 



138 When is the ovule orthotropous? 



