4o6 



NA TURE 



[Sept. 17, 1874 



pistil which is especially prepared for its reception. Wherever 

 the pistil projects beyond the stamens, it is obvious that a bee 

 alighting on the llower would come in contact first with the 

 former and subsequently with the latter. In flying from flower 

 to flower, therefore, she would generally fertilise each with the 

 pollen of one which had been previously visited. 



Fig. 8 represents the common Berberry, ff represent 

 the stamens, which lie close to the petals and almost 

 at right angles to the pistil {st), as shown in the figure. 

 The honey-glands (« 11) are twelve in number, situated in 

 pairs at the base of the petals, so that the honey rurs down into 

 the angle between the bases of the stamens and of the pistil. 

 The papillary edge o( the summit of the pistil [s /) serves as the 

 s'ignia. In open flowers of this kind it is of course obvious that 

 insects will dust themselves with the pollen and then carry it 

 with them to other flowers. In Berberis, however, both advan- 

 tages, the dusting and the cross-fertilisation, are accomplished by 

 a very curious contrivance. The bases of the stamens are highly 

 irritable, and when an insect touches them the stamens spring 

 forward (Fig. g) and strike the insect. The effect of this is not 

 only to shed the pollen over the insect, but also in some cases to 

 startle it and drive it away, so that it caiTies the pollen, thus 

 acquired, to another flower. 



In few flowers is the adaptation of the various parts to the 

 visits of insects more clearly and beautifully shown than in the 

 common white Dead Nettle (Laiiiiiuii album). Fig. 10. The 

 honey occupies the lower contracted portion of the tube 

 (Fig. 10, c a), and is protected from the rain by the arched upper 

 lip and by a thick rim of hairs. Above the narrower lower portion 

 the tube expands and throws out a broad lip (Fig. 10, w), 

 which serves as an alighting place for large bees, while the length 

 of the narrow tube prevents the smaller species from obtaining 

 access to the horey, whxli would be injurious to the flower, as it 

 would remove the souice of attraction (or the bees, without 

 effecting the object in view. At the base of the tube, moreover, 

 there is a ring of hairs, which prevent small insects from creeping 

 down the tulie and so getting at the honey. Lamium, in (act, 

 like so many of our other wild flowers, is especially adapted for 

 humble-bees. They alight on the lower lip (Fig. 10, ///), which 

 projects at the side so as to afford them a leverage by means of 

 which they may press the proboscis down the tube to the honey ; 

 while on the other hand the arched upper lip, in its size, form, 

 and position, is admirably adapted not only as a protection 

 against rain, but also to prevent tiic anthers (Fig. 10, a a) and 

 pistil (Fig. 10, St) from yielding too easily to the pressure of 

 the insect, and thus to ensure that it presses the pollen which it 

 has brought (rom other flowers against the pistil. 



The stamens do not form a ring round the pistil, as is so usual. 

 On the contrary, one st.imen is absent or rudimentary, while the 

 other four lie along the outer arch of the flower, on each side of 

 the pistil. They are not of equal length, as is usual, but one 

 pair is shorter than the other ; sometimes the inner pair, and at 

 others the outer pair being the longest. Now, why is this ? 

 Probably, as Dr. Ogle has suggested, because if the anthers had 

 lain side by side, the pollen would have adhered to parts of t!ie 

 bee's head which do not come in contact with the stigma, and 

 wculd therefore have been wasted ; perhaps also partly, as he 

 suggeits, because it would have been deposited on the eyes of 

 the bees, and might have so greatly inconvenienced them as to 

 deter them from visiting the flower. Dr. Ogle's opinion is 

 strengthened by the fact that there are some species, as for 

 instance the P'oxglove, in which the anthers are transverse when 

 immature, but become longitudinal as they ripen. 

 : Bat to return to the Dead Nettle. From the position of the 

 pistil which hangs down below the anthers, the bee comes in 

 contact with the former before touching the latter, and conse- 

 quently generally deposits upon the stigma pollen from another 

 flower. The small processes (Fig. 10, m) on each side of the 

 lower lip are the rudiments of the lateral leaves with which the 

 ancestors of the Lamium were provided. Thus, then, we see 

 how every part of this flower, is either, like the size and shape 

 of the arched upper liji, the relative position of the pistil and 

 anthers, the length and n:iriowness of the tube, the size and 

 position of the lower lip, the ring of hairs and the honey, adapted 

 to ensure the transference, by bees, of pollen from one flower 

 to another ; or, like the minute lateral points, is an inherit- 

 ance from more highly developed organs of ancestors. If we 

 compare Lamium with other flowers we shall see how great a 

 saving is eflected by this beautiful adaptation. The stamens 

 are reduced to four, the stigma almost to a point ; how gieat a 



contrast with the pines and their clouds of pollen ; or even with 

 such a flower as the Nymphsa, where the visits of insects are 

 secured, but the transference of the pollen to the stigma is, so to 

 say, accidental. Yet the fertilisation of Lamium is not less effec- 

 tually secured than in either of these. 



In this flower it would appear, as already mentioned, that the 

 pistil matures as early as the stamens, and that cross-fertilisation 

 is obtained by the relative position of the stigma, which, as will 

 be seen in the figure, hangs down below the stamens, so that a 

 bee bearing pollen on its back from a previous visit to another 

 flower would touch the pistil and transfer to it some of this 

 pollen before coming in contact with the stamens. 



In other species belonging to the same gi-eat group (Lab'at*) 

 the same object is secured by the fact that the stamens come to 

 maturity before the pistils have shed their pollen, and shrivelled 

 up before the stigma is mature. 



Fig. 1 1 represents a young flower of Salvia officinalis * in 

 which the stamens (a) are mature, but not the pistil (/), which 

 moreover from its position is untouched by bees visiting the 

 flower. The anthers as they shed their pollen gradually shrivel up ; 

 while on the other hand the pistil increases in length and curves 

 downwards, until it assumes such a position that it must come 

 in contact with any bee visiting the flower, and w'ould touch just 

 that part of the back on which pollen would be deposited by a 

 younger flower. In this manner self-fertilisation is effectually 

 provided against. There are, however, several other points in 

 which S. offiiiiialis differs greatly from the species last described. 



The general form of the flower indeed is very similar. We 

 find again, as generally in the Labiates, tlie corolla has the lower 

 lip adapted as an alighting board for insects, while the arched 

 upper lip covers and protects the stamens and pistils. 



In the present species, however, the back of the upper lip 

 shows a deep arch at the part x, and the front portion of the lip, 

 containing the stamens, is loftier than in Lamium, and does not 

 therefore come in contact with the back of the bee. In evident 

 correlation with this arrangement we find a very remarkable 

 difference in the stamens (Figs. 13 and 14). Two of the 

 stamens are minute and rudimentary. In the other pair the 

 two anther cells (Fig. 14, a a), instead of being as usual close 

 together, are separated by a long connection. Moreover, 

 the lower anther cell contains very little pollen, sometimes 

 indeed none at all. This portion of the stamen, as shown in 

 Fig. 13, hangs down and partially stops up the mouth of the 

 corolla tube. \\'lien, however, a bee thrusts its head into the 

 tube in search of the honey, this part of the stamen is pushed 

 into the arch, the connectives of the two large sta mens revolve 

 on their axis, and consequently the fertile anther cells are brought 

 down on to the back of the bee, as shown in Fig. 12. 



{To be coiitiniteii.) 



NOTES 

 The German Government has determined upon the erection 

 of a Sun Observatory (" Soniien-lVarte") upon a large scale at 

 Potsdam. Drs. Spoerer and Vogel have already been appointed 

 to undertake the telescopic and spectroscopic obsen'ations, and 

 the directorship has been offered to Prof. Kirchhoff, who, how- 

 ever, has declined it, as he is imwilling to leave Heidelberg. 



The International Congress of Orientalists was opened in 

 London on Monday, by an address from Dr. Birch. We hope 

 to give an account of the proceedings in our next number. 



We are glad to see that a contemporary not specially devoted 

 to science — the Montin^ Post — in an article on Dr. Hooker's 

 address at Belfast, points out to its readers that the majority of 

 the observations referred to could be made "by any intelligent 

 person without any scientific training," and expresses a hope that 

 " people who have the opportunities for cultivating, and leisure 

 for observing, will make collections of plants .... and add to 

 our stock of knowledge." At the same time it suggested these 

 as interesting subjects for observation : — " How much can plants 

 eat in twenty-four hours ? When do they eat most ? Under 

 what conditions of weather? &c. Indeed, tlie whole field is one that 



* The Pof>ular Science Kc^'icw for July 1869 contains a very clear and 

 interesting paper by Dr. Ogle ou this genus. ^ ,^^^^ 



