AN ENCYCLOPEDIA OF HORTICULTURE. 



507 



Stocks continued. 



separated and placed aside, because it has been ascertained 

 that the plants coming from the seeds situated in this 

 portion of the pod give eighty per cent, of single flowers. 

 They yield, however, greater variety than the others. 

 This plan of suppressing that part of the pod which 

 yields single flowers in the largest proportion, greatly 

 facilitates the recognition of the single-flowered plants, 

 because there remains to be eliminated from among the 

 seedlings only from ten to fifteen per cent." 



This separation of the single from the double-flowered 

 plants, M. Chate tells us, is not so difficult as might be 

 supposed. The Single Stocks, he explains, have deep green 

 leaves (glabrous in certain species), rounded at the top, 

 the heart being in the form of a shuttlecock, and the 

 plant stout and thickset in its general aspect; while the 

 plants yielding double flowers have very long leaves of a 

 light green colour, hairy, and curled at the edges, the 

 heart consisting of whitish leaves, curved so that they 

 completely inclose it. 



Such is the substance of M. Chate's method of securing 

 so large a proportion of double-flowered plants, and then 

 of separating them from the remaining single ones a 

 method which commends itself to tfce good sense of the 

 intelligent cultivator. 



Another plan for the separation of the single from the 

 double-flowered plants, in vogue amongst a class of cul- 

 tivators, is the degustation of the buds, that is to say, 

 the chewing of the young buds: the single plants can be 

 recognised by their crispness and greater consistence, and 

 can thus be weeded out. The disadvantage attending this 

 method is that the plants, single as well as double, must 

 all be grown up to the period when these buds are 

 tolerably well advanced. 



STOCK, TEN-WEEKS. A common name for 

 Matliiola aimua (which see). 



STOCK, VIRGINIAN. A common name for Mal- 

 colmia maritima (which see). 



STCECHAS. Included under Lavandula. 



STOKES' ASTER. See Stokesia cyanea. 



FIG. 542. STOKESIA CYANEA. 



STOKESIA (named in honour of Jonathan Stokes, 

 M.D., 1755-1831, the coadjutor of Withering in his 



Stokesia continued. 



arrangement of British plants). SIN. Cartesia. ORD. 

 Composites. A monotypic genus. The species is a hand- 

 some, sparingly - branched, greenhouse, erect, perennial 

 herb. It thrives in the open border during the summer 

 months. Propagation may be effected by seeds, or by 

 division of the roots. 

 S. cyanea (blue). Stokes 1 Aster, ft.-heads blue, lin. across, few 



or solitary, terminal, pedunculate ; involucre sub-globose,' the 

 outer scales prolonged into a leafy, bristly-fringed appendage, 

 the inner ones lanceolate and entire ; florets narrowly five-cleft ; 



pappus composed of four or five chaffy scales. Augus't. I. alter- 

 nate, smooth, lanceolate, entire or spinuloso-ciliate at base; 

 lower ones petiolate ; upper ones amplexicaul. Stem 1ft. to lift, 

 high. North America, 1766. See Fig. 542. (B. M. 4966.) 



STOLE, or STOLON. A branch arising from near 

 the base of the parent stem, resting on the soil, rooting 

 at the tip, and finally tending to form a new plant, 

 capable of independent growth when the branch is cut, 

 or dies away, between the terminal bud and the parent 

 plant. Certain modifications of Stolons have received 

 distinctive names, of which the more important are : 

 Offset, a short Stolon (e.g., Sempervivum), and Runner, 

 a very slender Stolon, with long, naked internodes (e.g., 

 Strawberry). 



STOLONIFEROUS. Bearing, or propagating by, 

 stolons, runners, &c. 



STOMA (plural, Stomata ; from stoma, a mouth). The 

 Stomata are little openings, or mouths, in the outer cover- 

 ing or epidermis of the green parts of plants, through 

 which they may be said to breathe. The air passes into 

 the plant from the outside, bringing with it Carbonic Acid 

 gas. This gas is broken up in the cells containing chloro- 

 phyl: all the Carbon, and half of the Oxygen, of the 

 Carbonic Acid are retained by the plant, to be built up 

 into starch, and other foods ; and half of the Oxygen 

 escapes from the plant into the outer air, through the 

 Stomata. The air passing out is loaded with vapour of 

 water evaporated from the cells of the leaf; and thus 

 there is a constant escape, through the Stomata, of water 

 from green parts of plants. The form and structure 

 of the Stomata do not vary much in vascular plants; 

 though many groups of these plants exhibit peculiarities 

 in the form and arrangement of the cells of the epidermis 

 that lie round the Stomata, and that are often called the 

 " neighbour-cells " ; but it is not necessary here to enter 

 upon a description of the latter. The Stoma, or opening, 

 lies between two sausage - shaped cells, called " guard- 

 cells," which are joined near the ends, but leave a space 

 between them in the middle. This opening leads into 

 an empty space between the cells, below the epidermis, 

 from which space crevices pass in all directions, opening 

 into larger ones among the loosely-arranged cells in the 

 middle of the leaf. There is a constant passage of gases 

 into and out of the cells through the thin cell-walls 

 that border the inter-cellular spaces, with results upon 

 the atmosphere as stated above, if green plants are 

 exposed to daylight. The guard-cells are usually green, 

 owing to the presence in them of chlorophyl. They thus 

 present a contrast to the ordinary cells of the epidermis, 

 which contain few, if any, chlorophyl-bodies in land 

 plants, except in Ferns, and a few others. The guard-cells 

 regulate evaporation from plants, since they swell when 

 full of sap, and become more convex, thus leaving 

 a wider opening between them when a plant contains 

 much sap and would benefit by the evaporation of some 

 of it. In dry weather, when there has been much evapora- 

 tion, the guard-cells contain less sap, and thus become 

 straighter, and leave a narrower slit; so that evapora- 

 tion becomes much slower through the Stoma when it 

 requires to be diminished in amount. Stomata seldom 

 occur on parts of plants habitually under ground, or under 

 water, where they would be useless. They are most 

 abundant on leaves, especially on the lower surface, ex- 

 cept in some Conifers, and a few other plants, in which 



