208 ELEMENTS OF SCIENCE 



leaves on either side. These foliar leaves are essentially 

 like the frond in structure and function save that they 

 bear no spores. 



But there are other foliar organs which grow forth 

 around delicate ramifications of the axis, and which form 

 what we know as " the flower." The green foliar organs 

 are separated from each other by interspaces consisting 

 of successive portions of the axis ; but these interspaces 

 are suppressed in the flower, so that its foliar organs are 

 all closely approximated. First comes a ring of green 

 foliar organs which are evidently but slightly modified 

 leaves. There are five of them, each of which is called a 

 sepal, while the whole five constitute what botanists 

 name the calyx. Then comes a ring of five more modified 

 and differently coloured leaves, each of which is called a 

 petal, the whole five petals forming what is known as the 

 corolla. Within the corolla are ten filamentary bodies 

 (stamens), each ending in an oval expansion, or anther, 

 which contains a fine yellow powder termed pollen. Each 

 particle of this powder is called a pollen-grain. Lastly, 

 in the centre of the flower is a single body known as the 

 pistil, whereof the upper portion is termed the style, at 

 the extremity of which is a somewhat modified surface, 

 spoken of as the stigma. The pistil is hollow and, if cut 

 open, will be found to contain small bodies named ovules, 

 which are attached to its inner surface by short stalks. 



The ovule is very far from being a simple cell, like the 

 oosphere of a 'fern. In the first place it is enclosed 

 in two coats, except at one point, called the micropyle, 

 while amongst the cells, of which the small body consists, 

 is one of larger size, termed the embryo sac, within which 

 again two thickenings arise, from the upper one of 

 which the future plant develops itself subsequent to im- 

 pregnation, while the lower one affords it nourishment. 



