254 TAKING UP OF POLLEN BY INSECTS. 



the pollinia uiay be seen peeping out of the longitudinal slits in the loculi with 

 their narrower extremities connected with the adhesive portion of the rostellum 

 (as in fig. 268 -). The manner in which this connection is established varies greatly, 

 according to the species, and cannot be discussed here; all we need note is the fact 

 that the union is so strong that the two pollinia are drawn out of their hiding-places 

 and carried away by any object which, coming into contact with the rostellum, 

 i-emoves the viscid mass from it. The Broad-leaved Helleborine (Epipactis lati- 

 folia), a plant of wide distribution in Europe, exhibits extremely well all the 

 pecuharities of Orchids above referred to (see figs. 268- and 268^). The upper 

 part of the labellum is excavated, and contains a copious supply of honey. Above 

 the labellum is the quadrangular stigma (fig. 268 ^) borne by the column, and sur- 

 mounting this is the wart-like and projecting rostellum (a wliite dot in the figure), 

 whilst the anther crowns the column. The two pollen-masses developed in the 

 anther are connected with the viscid portion of the rostellum. Fig. 268* shows 

 what the pollinia look like when they are drawn out of the anther. The honey 

 secreted in the cavity of the labellum is easily accessible to insects with short j)ro- 

 bosces, and the flowers of Helleborine are therefore much frequented by wasps. I 

 have selected Vespa Austriaca for illustration, as I have often observed wasps of 

 that species on the flowers. On alighting the insect holds on with its legs to the 

 embossed parts of the lip and proceeds to lick up the honey filling the cavity, 

 beginning at the bottom and woi'king up to the top. During the latter part of 

 the operation its forehead must inevitably come into contact with the viscid 

 projecting rostellum, which at once adheres to it (see fig. 268 ^). In withdrawing 

 from the flower, when the feast is over, the wasp draws the two pollen-masses 

 attached to the viscid rostellum out of the anther-loculi, and flies away into the 

 open air adorned with this curious head-dress (fig. 268 *). Not satisfied with the 

 meal afforded by a single flower, it straightway seeks another and behaves here 

 in the same manner as it did on the first occasion. During the time of flight 

 from one flower to another the pollinia, sticking to the wasp's forehead, undergo 

 a gradual tilting forward, the sticky gland remaining fixed at the same spot, but 

 the pollinia becoming depressed; as a consequence of this change in their position, 

 the pollinia are not shoved into the anther of the next flower the wasp visits, but 

 are pressed against the quadrangular stigma (see fig. 268 ''). This depression of the 

 pollinia is much better marked in many other common Orchids, however. 



In all essential respects the process above described is conunon to the majority 

 of Orchids where the labellum has a downward inclination and there is only a 

 single anther; but great variety prevails in respect of accessory details, as indeed 

 is to be expected, when we consider the wide divergencies existing in the forms 

 of the flowers and of tlieir insect-visitors. A brief i-eference to two of the most 

 sti'iking modifications is all we can give here. The greatest variation is exhibited, 

 as we said before, by the labellum and the x'ostellum. In some genera — in the 

 Twayblade (Listera), for example — the part of the lip which contains the honey 

 is not bowl-shaped, but in the form of a long, narrow furrow, and the secretion 



