The Elements of Botany Part 13

-- 5. ARRANGEMENT OF PARTS IN THE BUD.

276. =aestivation= was the fanciful name given by Linnaeus to denote the disposition of the parts, especially the leaves of the flower, before _Anthesis_, i. e. before the blossom opens. _Praefloration_, a better term, is sometimes used. This is of importance in distinguishing different families or genera of plants, being generally uniform in each.

The aestivation is best seen by making a slice across the flower-bud; and it may be expressed in diagrams, as in the accompanying figures.

277. The pieces of the calyx or the corolla either overlap each other in the bud, or they do not. When they do not overlap, the aestivation is

_Valvate_, when the pieces meet each other by their abrupt edges, without any infolding or overlapping; as the calyx of the Linden or Ba.s.swood (Fig. 277).

[Ill.u.s.tration: Fig. 277. Diagram of a flower of Linden, showing the calyx valvate and corolla imbricate in the bud, etc.]

_Induplicate_, which is valvate with the margins of each piece projecting inwards, as in the calyx of a common Virgin's-bower, Fig.

278, or

[Ill.u.s.tration: Fig. 278. Valvate-induplicate aestivation of calyx of common Virgin's-bower.]

_Involute_, which is the same but the margins rolled inward, as in most of the large-flowered species of Clematis, Fig. 279.

[Ill.u.s.tration: Fig. 279. Valvate-involute aestivation of same in Vine-bower, Clematis Vitialla.]

_Reduplicate_, a rarer modification of valvate, is similar but with margins projecting outward.

_Open_, the parts not touching in the bud, as the calyx of Mignonette.

278. When the pieces overlap in the bud, it is in one of two ways; either every piece has one edge in and one edge out, or some pieces are wholly outside and others wholly inside. In the first case the aestivation is

_Convolute_, also named _Contorted_ or _Twisted_, as in Fig. 280, a cross-section of a corolla very strongly thus convolute or rolled up together, and in the corolla of a Flax-flower (Fig. 281), where the petals only moderately overlap in this way. Here one edge of every petal covers the next before it, while its other edge is covered by the next behind it. The other mode is the

[Ill.u.s.tration: Fig. 280. Convolute aestivation, as in the corolla-lobes of Oleander.]

[Ill.u.s.tration: Fig. 281. Diagram of a Flax-flower; calyx imbricated and corolla convolute in the bud.]

_Imbricate_ or _Imbricated_, in which the outer parts cover or overlap the inner so as to "break joints," like tiles or shingles on a roof; whence the name. When the parts are three, the first or outermost is wholly external, the third wholly internal, the second has one margin covered by the first while the other overlaps the third or innermost piece: this is the arrangement of alternate three-ranked leaves (187).

When there are five pieces, as in the corolla of Fig. 225, and calyx of Fig. 281, as also of Fig. 241, 276, two are external, two are internal, and one (the third in the spiral) has one edge covered by the outermost, while its other edge covers the innermost; which is just the five-ranked arrangement of alternate leaves (188). When the pieces are four, two are outer and two are inner; which answers to the arrangement of opposite leaves.

279. The imbricate and the convolute modes sometimes vary one into the other, especially in the corolla.

280. In a gamopetalous corolla or gamosepalous calyx, the shape of the tube in the bud may sometimes be noticeable. It may be

_Plicate_ or _Plaited_, that is, folded lengthwise; and the plaits may either be turned outwards, forming projecting ridges, as in the corolla of Campanula; or turned inwards, as in that of Gentian Belladonna; or

_Supervolute_, when the plaits are convolutely wrapped round each other, as in the corolla of Morning Glory and of Stramonium, Fig. 282.

[Ill.u.s.tration: Fig. 282. Upper part of corolla of Datura Stramonium in the bud; and below a section showing the convolution of the plaits.]

Section IX. STAMENS IN PARTICULAR.

281. =Andrcium= is a technical name for the staminate system of a flower (that is, for the stamens taken together), which it is sometimes convenient to use. The preceding section has dealt with modifications of the flower pertaining mainly to calyx and corolla. Those relating to the stamens are now to be indicated. First as to

282. Insertion, or place of attachment. The stamens usually go with the petals. Not rarely they are at base

_Epipetalous_, that is, inserted on (or adnate to) the corolla, as in Fig. 283. When free from the corolla, they may be

[Ill.u.s.tration: Fig. 283. Corolla of Morning Glory laid open, to show the five stamens inserted on it, near the base.]

_Hypogynous_, inserted on the receptacle under the pistil or gyncium.

_Perigynous_, inserted on the calyx, that is, with the lower part of filament adnate to the calyx-tube.

_Epigynous_, borne apparently on the top of the ovary; all which is explained in Fig. 270-274.

[Ill.u.s.tration: Fig. 284. Style of a Lady's Slipper (Cypripedium), and stamens united with it; _a_, _a_, the anthers of the two good stamens; _st_, an abortive stamen, what should be its anther changed into a petal-like body; _stig_, the stigma.]

_Gynandrous_ is another term relating to insertion of rarer occurrence, that is, where the stamens are inserted on (in other words, adnate to) the style, as in Lady's Slipper (Fig. 284), and in the Orchis family generally.

283. =In Relation to each Other=, stamens are more commonly

_Distinct_, that is, without any union with each other. But when united, the following technical terms of long use indicate their modes of mutual connection:--

_Monadelphous_ (from two Greek words, meaning "in one brotherhood"), when united by their filaments into one set, usually into a ring or cup below, or into a tube, as in the Mallow Family (Fig. 286), the Pa.s.sion-flower (Fig. 260), the Lupine (Fig. 287), and in Lobelia (Fig.

285).

[Ill.u.s.tration: Fig. 285. Flower of Lobelia cardinalis, Cardinal flower; corolla making approach to the ligulate form; filaments (_st_) monadelphous, and anthers (_a_) syngenesious.]

[Ill.u.s.tration: Fig. 286. Flower of a Mallow, with calyx and corolla cut away; showing monadelphous stamens.]

[Ill.u.s.tration: Fig. 287. Monadelphous stamens of Lupine. 288.

Diadelphous stamens (9 and 1) of a Pea-blossom.]

_Diadelphous_ (meaning in two brotherhoods), when united by the filaments into two sets, as in the Pea and most of its near relatives (Fig. 288), usually nine in one set, and one in the other.

_Triadelphous_ (three brotherhoods), when the filaments are united in three sets or cl.u.s.ters, as in most species of Hyperic.u.m.

_Pentadelphous_ (five brotherhoods), when in five sets, as in some species of Hyperic.u.m and in American Linden (Fig. 277, 289).

_Polyadelphous_ (many or several brotherhoods) is the term generally employed when these sets are several, or even more than two, and the particular number is left unspecified. These terms all relate to the filaments.

_Syngenesious_ is the term to denote that stamens have their anthers united, coalescent into a ring or tube; as in Lobelia (Fig. 285), in Violets, and in all of the great family of Compositae.

284. =Their Number= in a flower is commonly expressed directly, but sometimes adjectively, by a series of terms which were the name of cla.s.ses in the Linnaean artificial system, of which the following names, as also the preceding, are a survival:--

_Monandrous_, i. e. solitary-stamened, when the flower has only one stamen,

_Diandrous_, when it has two stamens only,

_Triandrous_, when it has three stamens,