PLATE XXIII.-WHITE DEAD-NETTLE (Lamium album) and SAGE (Salvia). 



{Figures of Sage from Dodtl-Port, after II. Miiller.) 



Dead-nettle. 



... J he common white Dead-nettle owes, no doubt, much of its widespread character to the perfect adaptation of its structure to for- 

 mation by insects The contrivances for ensuring cross-fertilisation will now be glanced at The lower lip of the corol a is expandec 

 hus forming a platform for insects. The upper lip arches over the stamens like an umbrella, protecting them from rain, and pri ent n . 

 the pollen from being carried away, at the same time sheltering the tube of the corolla, at the base of which lies the honey The 

 ring of upwardly directed hairs near the bottom of the tube will exclude small insects from the honey. The stamens are arranged 

 in parallel series of different lengths, and thus the pollen is not widely dusted over the insect's body, but confined to parts where Ttwi 

 most easily come in contact with the stigma. The stigma, too, hangs down beneath the anthers, and the stigmatic surface is turned 

 outwards, so that any of the flower's own pollen falling down, will only fall upon the back of it, and produce no effect 



VVhen an insect visits a flower of this construction, it alights upon the platform, attracted by the white flowers peeping out from the 

 green foliage; and as it wedges its head into the tube for honey, the pollen on its back is sure to brush against the under surface of the 

 stigma As the stigma lies lower than the anthers, it will come against it first, and so leave the foreign pollen upon it When back- 

 ing out, the insect will receive a fresh coating of pollen from the stamens, and be ready to repeat the process over again on the next 

 nower it visits. 



Stem, Leaves, and Flowers — 

 Fig". 1. Stem, square. 



Leaves, opposite, and alternately on opposite sides of the square stem. 

 Figs. 2 and 3. Flowers in the axils of leaves; the tufts in each axil being a dichotomous cyme condensed. 



With a pair of scissors slit up the front face of the flower, that is, the ventral surface, and lay out the 

 parts so as to display interior. 

 Sepals, separating from each other about half way into long, thin points. 

 Petals, upper lip notched; lower lip with central lobe, and a little tooth at each side. 

 Stamens, attached to throat of corolla, but their fibro-vascular cords may be traced to the base, and thus their 



relative position to the other parts of the flower fixed. 

 Carpels, with forked stigma; the stigmatic surface turned away from the Anthers. 

 Diagram. — Plan of Flower — 



Calyx, bell-shaped, of five united Sepals — one dorsal, two lateral, and two ventral. 



Corolla, two-lipped; upper lip of two united Petals, and lower lip of three (the upper lip is divided in the Ground 

 Ivy, and the little teeth of the lower lip are known in some flowers to grow out into regular lobes; hence, 

 from this and their alternating position, the two lips together are considered five united Petals). 

 Andruecium, of four Stamens; two long and two a little shorter (in some instances a fifth rudimentary stamen is 



found). 

 Gyncecium, of two united Carpels. 

 Floral-Leaves — 



Fig. 4. Stamen, showing filament expanding into connective. 

 Fig. 5. Gyncecium. 



The ovary is four-lobed, and this might be taken as indicating four Carpels without an explanation. There are 

 really two carpels, as denoted by the bifid stigma, which meet by their edges in the middle, and each carpel bears two 

 ovules, thus making four altogether. The midrib of each carpel grows out towards the centre, and becomes attached 

 to it, thus making the double chamber into four. Then the dorsal side of each carpel, that is, the midrib portion, 

 grows excessively, so that the style becomes sunk in the middle, and apparently rises from the base of the ovary. 

 Fruit and Seed — 



Fig. 6. Fruit, consists of four little Nutlets. 



Seed, entirely taken up with Embryo. 



Fig. 7. Embryo, removed and enlarged. 



Sage. 



Figs. 8, 9, and 10. In Sage, the contrivances for cross-fertilisation are carried to even a higher degree of perfection than in Dead- 

 nettle, as the amount of fertilising material at command is less, there being only two stamens. The Figures will show 

 the arrangement of the parts better than any description, and a brief explanation will suffice. 



In Dead-nettle the two Anther-lobes were obliquely divided, but in Sage they are completely separated (Fig. 9). 

 The Connective diverges to such an extent that this separation takes place, and the upper anther-lobe only bears 

 pollen, while the lower is rudimentary and a mere pad An insect visiting the flower (as in Fig. 9) strikes against 

 this lower rudimentary lobe, and the upper anther-lobe swings round, dusting the insect's back with pollen. As an effectual 

 preventative against self-fertilisation, the anthers are mature before the stigmas are ready, and on ripening the stigmas 

 come to occupy the position formerly held by the anther-lobes, so that an insect carrying the pollen from one flower 

 will leave it on the stigma of another. In the Dead-nettle, which even flowers in winter and early spring, when 

 insects are either scarce or absent, the stamens may curve round and come in contact with the stigma, as has actually 

 been observed. Here self-fertilisation does sometimes occur, but in the Sage that is impossible. 



CLASSIFICATION. 

 Class. — Dicotyledon. 

 Division. — Gamopetalae. 

 Order. — Labiatse. 



Stem, square. 



Leaves, opposite. 



Inflorescence, condensed cymes. 



Corolla, two-lipped. 



Stamens, two long and two short. 



Carpels with four-lobed Ovary and bifid Style. 



Ovules, one in each lobe. 



Fruit, of four little Nutlets. 



Seed, without endosperm. 



