FERTILIZATION OF FLOWERS. 



four and five, certain of the chicora'cese expand ; between five 

 and six, the convolvulus tricolor appears ; about seven, the 

 lettuces, water-lilies, &c. ; about eight o'clock, a species ot 

 chick-weed ; about nine, the umbel-flowered marigold ; at ten, 

 the ice-plant; towards eleven, the purslain and the star of 

 Bethlehem ; about noon, most of the ficoides (fig-marigolds) ; 

 about sunset, the evening primrose ; between six and seven in 

 the evening, the marvel of Peru; between seven and eight, the 

 privet ; and about ten in the evening, a bind-weed, which garden- 

 ers call a morning-glory, because they always find it open when 

 they rise in the morning. 



7. When the flower has arrived at a certain period of its 

 development, the pollen formed by the anthers falls upon the 

 stigma, and in this way causes the fecundation of the ovules, 

 enclosed in the inferior part of the pistil ; frequently the stamens 

 are inclined towards the pistil that they may more conveniently 

 deposit the pollen ; for example, in the geraniums, the filaments 

 of the stamens are curved so that the anther rests upon the 

 stigma ; and in the nasturtium, the eight stamens are each in- 

 clined in turn for eight successive days to deposit the pollen on 

 the pistil in this way ; and at other times this species of dust is 

 cast into the air, and borne by the wind to the pistil of the same, 

 or of a neighbouring flower. 



8. It is easy to prove that the action of the pollen upon the 

 pistil is indispensable to the fecundation of the ovules and the 

 production of seeds which are developed in this organ. For 

 example, it is sufficient to cut off the stamens of an hermaphro- 

 dite flower to render it sterile (provided it be sufficiently removed 

 from other flowers in which the stamens have not been destroyed), 

 and when we have mutilated a flower in this way, it is sufficient 

 to cast upon its stigma some pollen taken from another flower of 

 the same species to make it produce seeds. In monoeceous plants 

 (that is, having flowers with stamens and flowers with a pistil 

 only on the same stalk), as the maize, it is only necessary to 

 remove the flowers with stamens to prevent the others from pro- 

 ducing seeds; and when the plants are dioeceous (that is, when 

 the stamens and pistils are borne on different stems) the fecun- 

 dating action of the pollen is still more evident ; it has been long 

 known that female date trees do not produce fruit, if they are 

 very distant from trees of the same species bearing flowers with 

 stamens ; and in this case they will not bear, if we are not care- 

 ful to dust over the branches, at the time of inflorescence, with 



7. How are flowers fertilized by the pollen ? 



8. What evidence have we that the pollen is necessary for the fecundation 

 jf flowers ? 



17 



