STRUCTURE OF THE FLOWER. 159 



We pass next to the consideration of the flower, and the 

 production of seed, recalling to your minds the general struc- 

 ture of a simple blossom. The outer circles of organs in 

 a wild rose or lily, for instance, constitute the envelopes : 

 these are the calyx and corolla, the protective organs ; with- 

 in these are the essential organs, by which alone seed is pro- 

 duced. The inner groups are made up of stamens and pis- 

 tils. The stamens are the organs which produce pollen, the 

 fertilizing dust. The pistils at their lower part, the ovary, 

 contain the ovules, or minute bodies which are to be fertil- 

 ized, and which will then become seeds. Without going into 

 details of structure unsuited to this occasion, I wish to im- 

 press upon you the important facts, that the cases containing 

 the pollen have a definite period at which they mature ; and 

 that they open, in some way, when they are ripe. At some 

 part of the pistil, usually its summit, there is a portion of the 

 surface more viscid than the rest. This is the stigma : upon 

 it the pollen falls, or is carried, and, there adhering, undergoes 

 a change by growth. A minute tube grows from it down to 

 the cavity of the pistil, where the bodies are, which are to 

 become seeds. The period of time which elapses before the 

 ovary is reached is very different in different species, extend- 

 ing from a single day, as in the crocus, to many weeks or 

 months in some orchids. As a result of contact between the 

 pollen-tube and a tiny cell, or vesicle, at the summit of the 

 ovule, impregnation takes place, and a germ or miniature 

 plant is produced. It may be further said, that different 

 plants occupy very different times for the maturing of the 

 seed after impregnation. The ovule ripens into the seed ; 

 and the ovary, frequently with some other parts near by, 

 ripens into the fruit. 



In many plants the stamens and pistils are in the same 

 blossoms : in others, like Indian corn for instance, the stam- 

 inate or male flowers are at the summit of the stalk, while 

 the pistillate or female flowers constitute the ears covered 

 with husks ; and from the coverings project the slender 

 thread-like styles with the stigmatic surfaces. In such a case 

 as this, the pollen falls from the clusters above, or it is borne 

 by the wind from clusters on other plants. The separation 

 of the sexes is sometimes even greater, the male and female 

 blossoms growing on different plants. There are some plants. 



