248. =The Deviations=, as they may be called, from the assumed type or pattern of flower are most various and extensive. The differences between one species and another of the same genus are comparatively insignificant; those between different genera are more striking; those between different families and classes of plants more and more profound. They represent different adaptations to conditions or modes of life, some of which have obvious or probable utilities, although others are beyond particular explanation. The principal modifications may be conveniently classified. First those which in place of perfect (otherwise called _hermaphrodite_ or bisexual) flowers, give origin to 249. =Unisexual, or Separated, or Diclinous Flowers=, _imperfect_ flowers, as they have been called in contradistinction to perfect flowers; but that term is too ambiguous. In these some flowers want the stamens, while others want the pistils. Taking hermaphrodite flowers as the pattern, it is natural to say that the missing organs are _suppressed_. This expression is justified by the very numerous cases in which the missing parts are _abortive_, that is, are represented by rudiments or vestiges, which serve to exemplify the plan, although useless as to office. Unisexual flowers are _Monœcious_ (or _Monoicous_, i. e. of one household), when flowers of both sorts or sexes are produced by the same individual plant, as in the Ricinus or Castor-oil Plant, Fig. 230. _Diœcious_ (or _Dioicous_, i. e. of separate households), when the two kinds are borne on different plants; as in Willows, Poplars, Hemp, and Moonseed, Fig. 231, 232. _Polygamous_, when the flowers are some of them perfect, and some staminate or pistillate only. [Illustration: Fig. 230. Unisexual flowers of Castor-oil plant: _s_, staminate flower; _p_, pistillate flower.] [Illustration: Fig. 231, staminate, and 232, pistillate flower of Moonseed.] 250. A blossom having stamens and no pistil is a _Staminate_ or _Male_ flower. Sometimes it is called a _Sterile_ flower, not appropriately, for other flowers may equally be sterile. One having pistil but no stamens is a _Pistillate_ or _Female_ flower. [Illustration: Fig. 233. Flower of Anemone Pennsylvanica; apetalous, hermaphrodite.] [Illustration: Fig. 234. Flower of Saururus or Lizard's-tail; naked, but hermaphrodite.] 251. =Incomplete Flowers= are so named in contradistinction to complete: they want either one or both of the floral envelopes. Those of Fig. 230 are incomplete, having calyx but no corolla. So is the flower of Anemone (Fig. 233), although its calyx is colored like a corolla. The flowers of Saururus or Lizard's-tail, although perfect, have neither calyx nor corolla (Fig. 234). Incomplete flowers, accordingly, are _Naked_ or _Achlamydeous_, destitute of both floral envelopes, as in Fig. 234, or