138 



PLANT BIOLOGY 



gourd, pumpkin, the plant is monoecious (" in one house "). 



When they are on different plants, e.g. poplar, cottonwood, 



bois d'arc, willow (Fig. 182), 

 the plant is dioecious ("in two 

 houses "). Some varieties of 

 strawberry, grape, and mul- 

 berry are partly dioecious. Is 

 the rose either monoecious 

 or dioecious ? 



Flowers in which the parts 

 of each series are alike are 

 said to be regular (as in Figs. 

 173, 174, 175). Those in 

 which some parts are unlike 

 other parts of the same series 



are irregular. Their regularity may be in calyx, as in 



nasturtium (Fig. 183); in corolla (Figs. 184, 185); in the 

 stamens (compare nasturtium, catnip, 

 Fig. 185, sage); in the pistils. Irregu- 

 larity is most frequent in the corolla. 



FIG. 182. CATKINS OF A WILLOW. 



A staminate flower is shown at s, and a 

 pistillate flower at /. The staminate 

 and pistillate are on different plants. 



FIG. 183. FLOWER OF 

 GARDEN NASTURTIUM. 



Separate petal at a. The 

 calyx is produced into a 

 spur. 



FIG. 185. 



FLOWER OF 



CATNIP. 



FIG. 184. THE FIVE PETALS 

 OF THE PANSY, detached to 

 show the form. 



