Plants in Relation to Man 



485 



'p --pollen grains 



anthers, and the pistil, with the receptive stigma and the ovary 

 containing the ovules or egg-cells, are the essential or repro- 

 ductive organs of the blossom. The pollen must be trans- 

 ferred to the stigma and thence to the ovules, if these are to 

 be fertilized and become seeds. 



Exercise. Study the several parts and their arrangement in any 

 of the typical flowers, such as the apple, peach, plum, tulip, or trillium. 

 Then select other flowers for comparison, and for the sake of bringing 

 out clearly the important features. 



Fertilization. The process of fertilizing the ovules in the 

 pistil can be outlined here only in a general way. It may be 

 studied more thoroughly with the aid 

 of a microscope. The chief features 

 of the process are illustrated diagram- 

 matically in Fig. 150. The pollen is 

 somehow transferred from the anther 

 to the stigma ; but it does not matter 

 for the present by what agency this 

 transfer is made, or whether the pollen 

 and ovules are produced by the same 

 individual plant or by different plants. 

 The latter is frequently the case, as 

 we shall find in later study. 



The stigma, which you find is 

 rough and often coated With a muci- 



laginOUS and Sweetish Substance, illustration of a simple pistil and 



holds securely any grain of pollen S^^J^M^ 



that may touch it. As SOOn as the all pollen grains except one to 



pollen grain is captured, it begins to ^^^^1 



grow, Sending down through the cell which unites with the egg 



stigma and the style into the ovary 



a very fine, hair-like tube, containing 



at the lower end two protoplasmic bodies, which are the 



essential male fertilizing elements. The pollen tube dissolves 



and utilizes as food the substance of stigma and style. Within 



ovary 

 "generative celt 



FIG. 150. A diagrammatic 



the embry ' 



