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 gourd, pumpkin, the plant is monœcious ("in one house"). When they are on different plants, e.g. poplar, cottonwood, bois d'arc, willow (Fig. 182), the plant is diœcious ("in two houses"). Some varieties of strawberry, grape, and mulberry are partly diœcious. Is the rose either monœcious or diœcious?

A staminate flower is shown at s, and a pistillate flower at p. The staminate and pistillate are on different plants.

Separate petal at a. The calyx is produced into a spur.

, detached to show the form.

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. Irregularity is most frequent in the corolla.