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Five groups of vessels run into the three sepals and two upper petals; three enter the labellure; and seven run up the great central column. These vessels are arranged, as may be seen, in rays proceeding from the axis of the flower; and all on the same ray invariably run into the same ovarian group: thus the vessels supplying the upper sepal, the fertile anther (A 1), and the upper pistil or stigma (i.e. rostellum S r), all unite and form the posterior ovarian group. Again, the vessels supplying one of the lower sepals, the corner of the labellure, and one of the two stigmas (S), unite and form the antero-lateral group; and so with all the other vessels.
Hence, if the existence of groups of spiral vessels can be trusted, and Dr. Hooker informs me that he has never known them to speak falsely, the flower of an Orchid certainly consists of fifteen organs, in a much modified and confluent condition. We see three stigmas, with the two lower ones generally confluent, and with the upper one modified into the rostellum. We see six stamens, arranged in two whorls, with one alone (A 1) generally fertile. In Cypripedium, however, two stamens of the inner whorl (a 1 and a 2) are fertile, and in other Orchids these two are represented in various ways more plainly than the remaining stamens. The third stamen of the inner whorl (a 3), when its vessels can be traced, forms the front of the column: Brown thought that it often formed a roedial excrescence, or ridge, cohering to the labellure; or, in the case of Glossodia,[1] a filamentous organ, freely projecting in front of the labellure. The former conclusion does not agree with my dissections; about Glossodia I know nothing. The two infertile stamens of the outer whorl (A 2, A 3) were believed by Brown to be sometimes represented by lateral excrescences on the labellure; I find these vessels invariably present in the labellure of every Orchid examined, even when the labellure is very narrow, or quite simple, as in Malaxis, HerininJure and Habenaria.
We thus see that an Orchid-flower consists of five simple parts, namely, three sepals and two petals; and of two compounded parts, namely, the column and the labellum. The column is formed of three pistils, and generally of four stamens, all completely confluent. The labellum is formed of one petal and two petalold stamens of the outer whorl, likewise completely confluent. I may remark, as making this fact more probable, that in the allied Marantaceae the stamens, even the fertile stamens, are often petalold, and partially cohere. This view of the nature of the labellum explains its large size, its frequently tripartite form, and especially its manner of coherence to the column, unlike that of the other petals.[2]
