TIIK STULXTURE OF TIIi: 1 LOW KR 325 



('i(g-ccU. Tlic iR'xt ^I'lRTatioii may be said to l)c;;in uith the 

 fertilised ef(g-cell, which develops into a plant embryo. 



The form of the embryo, at the sbige when it is ready to 

 be^iii independent life, mav be seen bv examinin«^ a ripe jx*a. 

 Within the seed-coat we find two thick, whitish bodies, which 

 occupy nearly the whole of the interior and are known as the 

 coti^lcdons. Retween them we can see a tinv root {thi' rad'ifU'\ 

 and a bud which will form the leafy shoot {the plumuU). Tlie 

 cotyledons are really the two first leaves of the young plant, 

 which have given up the usual form and appearance of leaves 

 in order to act as storehouses of food material for the vounjx 

 plant to draw upon before it has expanded its green leaves and 

 can nourish itself independently. 



In other wises, such as the wheat and the coffee-bean, the 

 embryo does not occupy the whole interior of the seed, but lies 

 more or less embedded in a store of food material which is 

 known as the endosperm. The cotyledons do not in these cases 

 store the food themselves, but they have the power of sucking 

 it out of the endosperm. 



The Flowering Plants are divided into two niain groups, the 

 Dicotyledons and Monocotyledons^ according as their seedlings 

 have two seed leaves, or only one. These two groups also differ 

 in floral characters. For instance, the dicotvle<lonous flower 

 has, as a rule, four or five parts in each whorl, and the jx?rianth 

 is often differentiated into calyx and corolla, while the 

 monocotyledonous flower has its parts in threes, and the 

 perianth is undifferentiated. 



We must now return to our description of flower structure, 

 and consider some of the chief modifications which the 

 general type may undergo. A typical flower contains 

 both gynaiceum and andrcucium, and is called hermaphroiiitc. 

 But it is possible to have tinisexuid flowers, which may be 

 either wholly male, or wholly female. This is brought about 

 by the suppression either of the gynicceum or andrcrcium 



