Anther Cells Research Articles

Self-fertilisation of Plants

IN NATURE, vol. xiv. p. 475, I find an abstract of Mr. Meehan's paper on the “self-fertilisation” of Browallia elata. When I first saw this paper in the Proceedings of the Philadelphia Academy of Natural Sciences, I suspected that the observation was incomplete and the inference hasty. It is therein stated that the densely bearded connectives of the upper anthers completely close the tube of the corolla with a bearded mass; that “no insect can thrust its proboscis into the tube except through this mass; and if it has foreign pollen adherent to it, it will be cleaned off by the beard; furthermore, the very act of penetration will thrust the anthers forward on to the pistil [meaning stigma], and aid in rupturing the pollen-sacs [opening the anther cells?], and securing self-fertilisation.” My inspection of the flower showed that the orifice of the tube was clearly pervious on the (morphologically) anterior side by a chink, which is nearly divided by a crust of the tube into two orifices, one exactly before each anther-cell; a hog's bristle, slightly moistened, oil being thrust down these passages in a freshly open flower, and then withdrawn, was found to have the inserted part well supplied with adherent pollen, so that it was not “cleaned off by the beard,” nor was it cleaned off by introduction into the orifice of a second flower.

Common Wild Flowers Considered in Relation to Insects* II

THE Common Heaths (Erica tetralix and E. cinerea) offer us another very ingenious arrangement. In E. tetralix (the Cross-leaved Heath), for instance, the flower is in the form of a bell (Fig. 15), which hangs with its mouth downwards, and is almost closed by the pistil (st), which represents the clapper. The stamens are eight in number, and each terminates in two cells, which diverge slightly, and have at their lower end an oval opening. But though this opening is at the lower end of the anther cells the pollen cannot fall out, because each cell, just where the opening is situated, touches the next anther cell, and the series of anthers thus form a circle surrounding the pistil and not far from the centre of the bell. Each anther cell also sends out a long process, which thus forms a series of spokes, standing out from the circle of anthers. Under these circumstances, a bee endeavouring to suck the honey from the nectary cannot fail firstly to bring its head in contact with the viscid stigma, and thus to deposit upon it any pollen derived from a previous visit; and secondly, in thrusting its proboscis up the bell, it inevitably comes in contact with one of the anther processes, which acts like a lever and dislocates the whole chain of anther cells when a shower of pollen falls from the open anther cells on to the head of the bee.†

Lotus corniculatus

MR. W. E. HART (NATURE, June 12) is quite right in correcting me on the subject of the fertilisation of Lotus corniculatus. It is the outer whorl of stamens, those opposite the calyx teeth, which continue to grow after the others, and which have their filaments dilated at the top so as to thrust the pollen out of the long sharp tube of the keel. I should scarcely have thought it necessary to acknowledge his courteous correction, if it were not for the following question and answer: How is it, then, that the pollen of the inner and shorter whorl of stamens, which discharge their pollen at the same time as the outer whorl, gets pushed out by the filaments of the outer whorl, since the anthers of the inner whorl lie below the summits of the filaments of the outer whorl? The answer is curious: In the early bud, before the anther cells begin to open, the inner whorl is obviously shorter than the outer whorl, so that the anthers of the former lie in a regular row entirely below the anthers of the latter, apparently for the convenience of close packing in the narrow closed flower. As the anther cells begin to open, which is just before the flower opens, the stamens of the inner whorl grow and approach very nearly in height to the stamens of the outer whorl; and as they shed their pollen from the summit of the anthers, their pollen comes out above the dilated tops of the filaments of the outer whorl, so that it can be pushed forwards by those filaments along with the pollen of their own anthers. The filaments of the inner whorl then wither and become comparatively short, while those of the outer whorl continue to grow, dilate, and stiffen, so as to do the work for all the pollen of both whorls. In the mature opened flower the difference between the two whorls becomes more marked than ever. If I am right, Mr. Hart's detection of my blunder leads to the notice of a curious instance of economy of space and of mechanism.