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Bot Zeit 1863 p. 241

Supplementary remarks on the fructification of some of the Orchideæ by L. C. Treviranus.

One of the most important parts of Ch. Darwin's excellent work on the fructification of orchideous plants is that which treats of Ophrys apifera and some other species nearly related to it. The author had

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not been able however at the time when he published his work [1862, Orchids], to solve a difficult question concerning an important exception from a rule about the way of action of the different parts of the flower, which otherwise appears almost universal.

It will not therefore, I hope he thought forward on my part to make known some facts which I have

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learnt concerning this subject since the publication of Mr. Darwin's work. I state them in the hope that others also who may have studied the subject will not keep back the results of their observations.

I must begin by stating that the doubts which I have expressed in some of my former writings concerning the existence of a good specific distinction between Ophrys apifera Huds.

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and V. arachnites Murr. Syst Veg. must not prevent us from acknowledging these two plants as distinct and constant forms, as modifications or varieties of the same species. I had not then been able at the same time to study and compare both forms alive, but I have since had an opportunity of doing so, and have found a decided, though not always conspicuous difference in the length and direction of the gynostem

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in the inner lobes of the perianth, (Perianthzipfeln) in the lobes of the labellum and in the appendage of the lower lobe (Endlappens) Seb. Vaillant has distinguished these two forms in an excellent manner. Seine Orchis fucum referens (Botan. Paris t. XXX S. 9, 9a) is Ophrys apifera – his Orchis araneam referens (t. ead. f. 10-13) clearly Ophrys arachnites. The last mentioned flower has been

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well drawn by Rivinus (Irregul hexap. t. xiii f. 3) as Orchis fucum referens.

Of the coloured drawings which I have seen, the best Ophrys apifera is by W. Curtis (Fl. Londin. I t. 15) the best V. arachnites by Reichenbach (Pl crit IX f. 1162-65. Ophr. fuciflora.)

What makes it peculiarly interesting carefully to examine and compare these two forms is the different way in which the organs of fructification

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act in producing fructification. It caused Mr. Darwin much astonishment to find in the same flower contrivance for directly opposite ends." (p. 70) namely for self-fertilisation and for fertilisation through the agency of insects, as in other orchideous plants.

Owing to bad materials and very unfavourable weather, my observations last year produced but few and unimportant results; and I should have been even

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less successful this year (for a wire fence which the present authorities of our botanical gardens have had put up round the bed which contains our indigenous orchids entirely prevented my working at them) had not my friend Dr. Basbach in Trier kindly sent me 40 specimens of Ophrys apifera and V. arachnites – all of which reached me alive and in excellent condition.

In these specimens I have been able thoroughly to

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watch the working of the different organs from the first opening of the flower to its setting seed and consequent withering.

Of Ophrys apifera, I must remark in the first place that the shifting of the pollinia the first accurate description of which was given by Curtis, is also mentioned by Gaudin, who writes (speaking of this flower) ("Massæ pollinis longius pedicellatæ, et retinaculo adhaerentes, extra loculum

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saepius dependent.") Fl. Helvet V. 460)

When the flower had completely opened I found in most cases the pollinia the long and tender stalks of which were still fixed in their places by the glands, separated from the anther and in a trembling motion.

But whether the former was caused by the slight motion in transporting the flowers, through their being shaken by the wind or

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through their having been visited by insects, it is impossible for me to say. I certainly could find no trace of insects having visited the flowers.

On touching one or both of the glands with a pointed instrument, I have several times succeeded (as Mr. Darwin has done under similar circumstances, p. 69) to withdraw the caudicle with the pollinia but the frequent failure of this experiment proved

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the sensitiveness of these parts to be decidedly less that is generally the case with Orchids.

In those flowers also which had been open some time the pollinia were still fixed in their places by means of their caudicles; but they were bent downwards so as to reach to the rim of the scar (Narbenrande) and in dome cases came down even lower.

In flowers somewhat older still, I found that the pollinia

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though still attached to the rostellum were, with their club like parts, glued to the scar. They were most of them of irregular shape, some of the lobes (Lãppchen) of the pollen masses having got loosened.

Of 18 spikes of Ophrys apifera which I examined bearing from 3-8 flowers each, most of the ovaries were swelling (fructification therefore had taken place) and in every case I found some pollen grains on the

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scar. These pollen grains had been brought there by means of the bending of the caudicles which still were fixed to the rostellum. The pollen masses were of different sizes and were covered with a white mould of shining threads.

These threads, I feel convinced were pollen tubes - for it is extremely improbable that in the open air mould should have been formed on all these separate flowers –but unfortunately the

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weakness of my eyes made it impossible for me to ascertain the fact.

I also found that in this stage of the flower the gynostem which whilst the flower is young is separated from the labellum, had considerably approached it and was in some cases even touching it. This, I believe must have assisted in the process of fructification.

With Ophrys arachnites my observations led to very different results. In this

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flower the pollinia are easily withdrawn by means of a needle or other pointed instrument; the column with the anther is, compared with the size of the labellum, shorter, less bent, and less beak shaped; and the caudicle of every pollen grain is shorter and less elastic than in Ophrys apifera.

This seems to be the cause that the pollinia do not of themselves fall out of the anther – or at least do so but very rarely. I have

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only once or twice found pollen grains glued to the scar and in these cases fructification had taken place – a fact worthy of notice as the production of seed by this Ophrys is of very rare occurrence.

That however under different circumstances (probably through the agency of insects) fructification would take place seems to be proved by observations made by Brotero on Ophrys Scolopax, a flower differing very little, if at all, from

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Ophrys arachnites. Brotero says (Phytogr. Lusitan I. 10)

"Antheræ/ i.e. the pollinia) nunquam e loculìs suìs exeunt, sed ibi persistunt virescentes, quamdiu stigma viget, etsi tunc floris integumenta etc. emarcida sint: tamen capsula et sermina increscunt, quorum nonnulla maturitatem adipiscuntur."

Thus the conclusions at which I have arrived after a careful study of these two forms entirely agree

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with the results of Mr. Darwin's observations.

Though nature seems to have provided in Ophrys apifera the means by which in most orchideous plants fructification is brought about, yet in by far the greater number of cases this Ophrys fertilises itself – because contrary to the general rule from their anthers and afterwards, through the bending of their slender caudicles, are deposited on the scar, neither of

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which is the case with Ophrys arachnites. With the latter on the contrary insect agency seems to be indispensable if fructification is to take place. It is probably because of the absence of this insect agency that this plant so rarely produces seed –but on this head further observations must be made.

To these communications which I thought to owe to the eminent observer of orchideous plants, I now add some few remarks

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concerning some other indigenous species of that family.

What is said by Mr. Darwin of the phenomena in the male element of fructification in Orchis (Anacamptis) pyramidalis concerning the disk and the altered position of the caudicles I can entirely corroborate.

The saddle shaped disk clings tightly round the pointed instrument by which it is withdrawn from the rostellum, immediately afterwards the

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two pollinia perform their slow diverging movement and at last remain at the same level with the saddle.

but in the drawing representing the flower at the moment when the phenomena just mentioned are taking place (p. 22 of Mr. Darwin's work) there are two not unimportant mistakes.

In the first place: the two side lobes of the scar should meet in the middle (als Continuum) whilst in the drawing they appear to join

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the raised part (Höcker) of the labellum.

Secondly: the small club shaped swellings situated between the anther and the side expansion of the scar have both been omitted.

Nees (Gen. Fl. germ. V. 5-8) justly calls these two protuberances the "Staminodien" but he represents them as if they were situated on the margin of the scar itself which is not the case.

I have watched a healthy

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spike of Orchis (Himantogloss) hircina bearing 41 flowers.

The plant was growing in a very unfavourable situation and consequently only about half the flowers produced seeds. In four of these I found pollen grains on the scar the transportation of which it had been impossible to watch.

It was interesting to observe (though it is a well known fact) how in most of the flowers which had been left without fructification the perianth and particularly

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the labellum did not wither nearly as soon as was [those] in the flowers which had been fertilised.

Schkuhr (in Handb. III p. 210) states of Epipactis palustris that the gland (Safbläschen) which joins the two stamens attaches itself to the overlying lip; that at the opening of the flower this caused the stamens to be drawn out of their anthers and to be placed before the scar; and that thus fertilisation is effected.

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Mr. Darwin seems to admit at least an approach to such a self acting withdrawal of the pollinia; and he thinks that there is no subsequent movement of the pollinia. I have examined a considerable number of spikes of this beautiful Orchis and I have found that in the perfectly open flower the pollinia were lying in their anthers exactly as before the opening of the flower.

In the greater number of cases the gland projected

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from the rostellum in the shape of a minute shining globe; and if I touched this globe with a needle the pollinia were fastened to it by means of the disks.

The rostellum flattened itself, but it did not sink down, nor did the anthers bend backwards as described by Mr. Darwin.

The pollinia on the other hand, without being furnished with a caudicle, performed the usual movement

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of Orchids with caudicles: they gradually approached my needle and in some cases sank down low enough to touch it.

If afterwards I inserted the needle with the pollinia attached to it, into a fresh flower between the gynostem and the labellum, a large portion of the pollen grains remained glued to the shining and sticky surface of the scar.

Moreover of 17 flowers

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from which the pollen had been removed, 4 had had pollen grains placed on their scars and had in consequence set seed.

I feel convinced therefore that in this case also insect agency is necessary for the production of fructification

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