42 



OVULE. 



carpellary leaf; the dissepiments being the partitions 

 of an ovarium formed by the united sides of the carpel- 

 lary leaves (d d fig. 40) : so it follows that a simple ova- 

 rium has no dissepiments. 



230. The ovule is a minute body attached to the pla- 

 centa, and contained within the cavity of the ovarium, 

 afterwards becoming the seed of the plant, whilst the 

 ovarium itself becomes the fruit vessel. 



231. In the fully developed state the ovule may be 

 said to consist of two parts its coats, and the nucleus 

 contained within them. 



Fig. 42. 



232. At first the nucleus exists alone as a very mi- 

 nute conical protuberance (a A) ; soon a swelling at the 

 base of it (b A) is seen to take place, which gradually 

 enlarges and extends itself around the nucleus in the 

 form of a covering (as at b B), but remains open at 

 the top : whilst this has been going on, a second swell- 

 ing (c A) has arisen, which extends itself in like manner 

 all over the other one and the nucleus within it, (c c) 

 remaining like the last open at its extremity. The nu- 

 cleus has now formed its two cbats ; the outermost or 

 last formed one (c) being called the primine, and the 

 innermost and first formed (6) the secondine ; the open- 

 ing of the primine (d c) is termed the exostome, and 

 that of the secondine (e b), endostome, and these exist 

 from the very first period of the formation of the coats. 



233. In by far the greater number of plants the ovule 

 has two coats, though in some exogens it 'has but a 

 single one, which is termed by Schleiden, integumen- 

 tum simplex. In some few examples it has likewise 

 been lately shown that the nucleus has no true coats at 



