HOW PLANTS GROW. 225 



the stigma never. Sometimes there may be more than one carpel. 

 This may be quite apparent, as in Buttercup, or they may be so 

 united that the ovaries form only one cavity — appareiitly^ therefore, 

 only one carpel, as in Primrose, whereas there are really five. 

 With this we have nothing to do now. The fact to remember is 

 this : that the ovary contains one (or there may be very many) 

 minute body attached to its inner wall, termed an ovule. This, 

 when " ripe," becomes the seed. This ovule is the essential element 

 that is to be fertilized. 



We must look yet more closely at both pollen-grain and ovule 

 to understand what work is assigned to each. 



A pollen-grain consists of a cell with tivo coats, and possessing 

 protoplasmic contents. The inner coat is entire ; the outer is 

 perforated by minute apertures, and often very exquisitely orna- 

 mented by spines and the like, as all my readers probably know. 

 Through these apertures in the outer coat, the inner one is able, 

 under certain conditions, to penetrate and send out a process 

 called a pollen-tube, which grows in length according to need. 

 To enable the inner coat to penetrate the outer, moisture is 

 needed. This is found in the moist cellular stigma, to which 

 the pollen-grains are carried from the anther-cells by the action of 

 gravity, by the wind, or by insect agency. This transferefice of 

 the pollen to the stigma is absolutely essential. Wlien once there, 

 the pollen-tube (or tubes) increases in length, nourished by the 

 stigmatic fluid, and penetrating the conducting-tissue of the style, 

 finds its way down this style into the ovary, and finally into the 

 ovule. 



An Ovule is at first, roughly speaking, a minute nodule of cellu- 

 lar tissue, growing on the wall of the ovary, at a spot called the 

 placenta. (This term is used to express the point of attachment 

 of an ovule, or of a set or row of ovules, to the ovary-wall; on 

 opening a pea-pod, each seed, or ripened ovule, is seen attached 

 to its own placenta.) A Funiculus, or "little cord," attaches 

 the ovule to its placenta. Presently, a double coat grows up 

 around the developing ovule, covering it entirely except at its 

 apex, where a tiny hole is left, called the Micropyle (meaning in 

 Greek a little gate or door). The original cellular mass inside 

 the coats is the Nucleus. 



