74 



SCIENCE PRIMERS. 



[xix. 



XIX. THE OVULE. 



113. The ovule is a minute body enclosed in the 

 ovary, and destined, after being fertilized by the pollen, 

 to become a seed, and to contain an embryo or 

 plantlet. There may be one, few, or many ovules in 

 an ovary; and if there are two or more, all, or a 

 few, or one only, of these may be fertilized and 

 become a seed. 



114. In its earliest stage the ovule consists of a 

 nucleus, which is a most minute swelling of cellular 

 tissue formed on the placenta (Par. no). Next a ring 

 of cellular tissue grows up around the base of the 

 nucleus and all but envelops it, leaving a canal or hole 

 (micropyle). Often a second ring forms at the base 

 of the first, and is similarly developed into an outer 

 covering. A vascular bundle (Par. 9) runs from the 

 edge of the carpellary leaf through the placenta into 



FIG. 54- Growth of ovule of celandine : a, nucleus ; b, first formed covering ; 

 c, second covering very greatly enlarged. 



the ovule, reaching the base of the nucleus, and is 

 concerned in its nutrition and in that of the seed. 



115. The ovule may be straight, or it may grow 

 obliquely, or it may as it were turn round on itself by 

 the greater growth of one side, so as to become com- 



