Page:Popular Science Monthly Volume 15.djvu/27

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17
CLEWS IN NATURAL HISTORY.

some multiple of that number) in the pistil. Where there appears to be a lack of this numerical correspondence, the botanist concludes that some violation of the law of symmetry has taken place, and that some parts or organs which should normally have been developed have been altered or suppressed. His reasoning, in fact, proceeds on the plain basis of first establishing, through experience, the normal number and condition of parts in the flower of any given order of plants, and of thereafter accounting by suppression or non-development for the absence of parts he expected to have been represented.

Now, in the snapdragon tribe, we find, as a general rule, five parts in the calyx, five petals in the corolla, but only four stamens. Such a condition of matters is well seen in the flower of frog's mouth (Antirrhinum), where we find four stamens, two being long and two short

170px
Fig. 2.

(Fig 2, A s1 s2), as the complement of the flower. We account for the absence of a fifth stamen by saving it is abortive. But a natural reflection arises at this point, in the form of the query, Have we any means of ascertaining if our expectation that a fifth stamen should be developed is rational and well founded? May not the plant, in other words, have been "created so?" Fortunately for science, Nature gives us a clew to the discovery of the truth in this as in many other cases. In one genus of these plants (Scrophularia), we find a rudiment of a fifth stamen (Fig. 2, Bs), and in snapdragon itself this fifth stamen becomes occasionally fully developed; while another plant of the order (Mullein) possesses five stamens as its constant provision. Unless, therefore, we are to maintain that Nature is capricious beyond our utmost belief, we are rationally bound to believe that the rudimentary fifth stamen of Scrophularia, and the absent fifth stamen of other plants of its order, present us with an example of modification and suppression respectively. The now rudimentary stamen is the representative of an organ once perfect and fully developed in these flowers, and which it perpetuated by the natural law of inheritance until conditions, to be hereafter noticed, shall have caused it to entirely disappear. The case for the natural modification, and that against the imperfect creation of such flowers, is proved by an ingenious experiment of Kölreuter's, upon plants which have the stamens and pistils situated in different plants, instead of being contained in the same flower, as is ordinarily the case. Some staminate or stamen-possessing flowers had the merest rudiment of the pistil developed, while another set had a well-developed pistil. When these two species were "crossed" in their cultivation, the "hybrids" or mule progeny thus produced evinced a marked increase in the development of the abortive organ. This experiment not only proved that, under