THE FLOWERING PLANT. 103 



FIG. XXI. A much older embryo of the same plant, at this stage quite green. 



The curvature of the cotyledons becomes intelligible on considering the natural position 

 of the embryo, shown at ii. in Fig. XVII. In life, the cotyledon marked* overlay its fellow, 

 as indicated by the dotted lines in Fig. XVII., thus hiding the apex from view. A. 3. 



FIG. XXII. Median longitudinal section of the fruit of Potamogeton (the Broad Pond- 

 weed), to show the relations of the endosperm to the embryo. Alcohol and weak glycerine. 

 A. 2. 



Each fruit of the above plant contains but one embryo, and if, holding the fruits between 

 the finger and thumb, the sides are sliced away, most satisfactory preparations can be 

 readily obtained. 



FIG. XXIII. A portion of the above more highly magnified, showing the nuclei of the 

 endosperm, and the embryo in detail. D. 4. 



The distinctive characters of the Monocotyledon embryo are here di'awn, as compared 

 with those of the Dicotyledon represented in Fig. XXI. 



