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Cruger saw a "continual procession" of bees thus crawling out of their involuntary bath. The passage is narrow, and is roofed over by the column, so that a bee, in forcing its way out, first rubs its back against the viscid stigma and then against the viscid glands of the pollen-masses.
Now at last we see the full use of every part of the flower, of the water-secreting horns of the bucket half-full of water, which prevents the bees from flying away, and forces them to crawl out through the spout, and rub against the properly placed viscid pollen-masses and the viscid stigma.
The pollen-masses are thus glued to the back of the bee which first happens to crawl out through the passage of a lately expanded flower, and are thus carried away. Dr. Cruger sent me a flower in spirits of wine, with a bee which he had killed before it had quite crawled out, with a pollen-mass still fastened to its back.
If you will gather some of these orchids during your next spring walk in the woods, and will put a pencil down the tube to represent the head of the bee you may see the little box open, and the two pollen-masses cling to the pencil.
I am glad to find that so high an authority as Professor Flower has come to this same conclusion. The extraordinary cases given in a former chapter, of widely different fishes possessing electric organs of widely different insects possessing luminous organs and of orchids and asclepiads having pollen-masses with viscid discs, come under this same head of analogical resemblances.
Schlimii × Cyp. longiflorum; curious as the single instance yet noted in which seedlings turn out identical, whichever parent furnish the pollen-masses. In every other case they vary when the functions of the parents are exchanged. For a long time after 1853, when serious work begun, Messrs. Veitch had a monopoly of the business.
In other orchids the threads cohere at one end of the pollen-masses; and this forms the first or nascent trace of a caudicle. That this is the origin of the caudicle, even when of considerable length and highly developed, we have good evidence in the aborted pollen-grains which can sometimes be detected embedded within the central and solid parts.
No orchids, however, give more material for study; on this account Catasetum was a favourite with Mr. Darwin. It is approved also by unlearned persons who find relief from the monotony of admiration as they stroll round in observing its acrobatic performances. The "column" bears two horns; if these be touched, the pollen-masses fly as if discharged from a catapult.
Nearly all our orchidaceous plants absolutely require the visits of insects to remove their pollen-masses and thus to fertilise them. Humble bees alone visit red clover, as other bees cannot reach the nectar.
Many of our orchidaceous plants absolutely require the visits of moths to remove their pollen-masses and thus to fertilise them. Hence I have very little doubt, that if the whole genus of humble-bees became extinct or very rare in England, the heartsease and red clover would become very rare, or wholly disappear.
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