Among monocotyledons Convallaria majalis may be mentioned as very liable to suffer diminution in the number of its carpels, either separately or in association with other changes.[473]
Meiophylly of the flower as a whole.—In the preceding sections a reduction in the parts of each individual whorl has been considered without reference to similar diminution in neighbouring verticils. It more commonly happens, nevertheless, that a defect in one series is attended by a corresponding imperfection in adjoining ones. Thus trimerous fuchsias and tetramerous jasmines may frequently be met with, and Turpin describes a tetramerous flower of Cobæa scandens. Perhaps monocotyledonous plants are more subject to this numerical reduction of the parts of several verticils than are other flowering plants. Thus, in both Lilium lancifolium and L. auratum the writer has frequently met with pentamerous flowers. In Convallaria maialis a like deviation not unfrequently occurs.[474] M. Delavaud has recorded a similar occurrence in a tulip.[475]
Dimerous crocuses may also sometimes be met with. In one flower of this nature the segments of the perianth were arranged in decussating pairs, and the four stamens were united by their filaments so as to form two pairs.
M. Fournier mentions something of the same kind in the flower of an Iris.[476]
Orchids seem peculiarly liable to the decrease in the number of their floral organs. Prillieux[477] mentions a flower of Cattleya amethystina wherein each whorl of the perianth consisted of two opposite segments.
The same observer has put on record instances of a similar kind in Epidendrum Stamfordianum. In one flower of the last-named species the perianth consisted of one sepal only, and one lip-like petal placed opposite to it.[478] Morren[479] describes a flower of Cypripedium insigne, in which there were two sepals and two petals. Of a similar character was the flower found by Mr. J. A. Paine, and described in the following terms by Professor Asa Gray in the 'American Journal of Science,' July, 1866:—"The plant" (Cypripedium candidum) "bears two flowers: the axillary one is normal; the terminal one exhibits the following peculiarities. The lower part of the bract forms a sheath which encloses the ovary. The labellum is wanting; and there are two sterile stamens, the supernumerary one being opposite the other, i.e. on the side of the style where the labellum belongs. Accordingly the first impression would be that the labellum is here transformed into a sterile stamen. The latter, however, agrees with the normal sterile stamen in its insertion as well as in shape, being equally adnate to the base of the style. Moreover, the anteposed sepal is exactly like the other, has a good midrib and an entire point. As the two sterile stamens are anteposed to the two sepals, so are the two fertile stamens to the two petals, and the latter are adnate to the style a little higher than the former. The style is longer than usual, is straight and erect; the broad, disciform stigma therefore faces upwards; it is oval and symmetrical, and a light groove across its middle shows it to be dimerous. The placentæ, accordingly, are only two. The groove on the stigma and the placentæ are in line with the fertile stamens.
Here, therefore, is a symmetrical and complete, regular, but dimerous orchideous flower, the first verticil of stamens not antheriferous, the second antheriferous, the carpels alternate with these; and here we have clear (and perhaps the first direct) demonstration that the orchideous type of flower has two stamineal verticils, as Brown always insisted."
Fig. 198.—Regular dimerous flower of Calanthe vestita.