256 THE SECOND BOOK OF BOTANY. 



was again fertilized by pollen, sent through the post. 

 The date is a dioecious tree, upon which the Eastern 

 countries depend for food. They suspend panicles of 

 <3 flowers near the single $ ones, to insure a crop of 

 the fruit. One of the ways in which these people 

 make war is, to destroy the $ date-trees ; the ? ones 

 are, of course, barren, and famine ensues. 



The usual time of fertilization is when the flower 

 is most perfect in its colors and fragrance. In the 

 course of Nature there are many ways in which the 

 pollen reaches the stigma. Either the stamens are 

 longest, and it falls upon the stigma below, or, if 

 shortest, the flower droops, as in the fuschia, and 

 then, also, the pollen falls upon the stigma, or it may 

 be thrown upon the stigma by spontaneous jerks of 

 the stamen, or the anthers burst with violence, and 

 so produce the same result. Pollen is also wafted by 

 the winds from flower to flower, or conveyed by in- 

 sects in their explorations for honey. In such plants 

 as orchids, where the pollen is in masses, self-fertili- 

 zation is impossible; the pistil can be acted upon 

 only by pollen brought to it from other plants. By 

 these various means pollen of all sorts is distributed 

 upon all sorts of flowers, but only that of the same, 

 or of nearly-related species, takes effect. 



You know the structure of pollen-grains, and that 

 the stigma is a mass of moist, cellular tissue, without 

 epidermis. Landed upon this conductive tissue, the 

 pollen-cell absorbs moisture, and its elastic in tine 

 swells, and pushes through the openings, or thin 

 places of the more rigid ex tine, protruding a sort of 

 tube, which grows downward, into the spongy centre 

 of the style, till it reaches the ovary. Here it is met 



