820' THE DISTRIBUTION OF SPECIES BY OFFSHOOTS. 



touches the soil, aud the result is that closely-crowded groups of new plants grow 

 up round it. The same thing may be observed in Chloropliytum comosum, a native 

 of the Cape often cultivated as a basket plant by gardeners under the name of 

 Conhjline vivi'para. In this plant leafy shoots are very regularly developed in the 

 floral region instead of flowers, and as these increase in size and become heavier, the 

 long, comparatively slender and very supple stem which bears them sinks down 

 so that the sprouts are suspended on a green thread. If the ground below is 

 suitable the pendent shoots which have meanwhile developed roots may settle 

 there. If they do not come into contact with any suitable soil they remain a long 

 time swaying in the air, growing and themselves forming long, thin stalks in their 

 turn in whose floral region fresh, leafy sprouts with roots arise, and years after 

 three or four generations of shoots connected together by a slender green stalk may 

 be seen hanging down for the length of a metre. At length one or other of the 

 swaying and wind-tossed sprouts strikes firm ground and takes root, separating 

 itself from the old plant, or it falls like the fruit from a tree and roUs down below 

 until it finds a place of settlement possibly at a considerable distance from the old 

 plant. 



Among the Rushes also there are many species which develop pendent sprouts. 

 In one species which is very widely spread over Northern Europe, viz. Juncus 

 supinus, it is much more usual to find sprout-like ofishoots in the floi'al I'egion than 

 flowers. In many of the Saxifrages of the far North, viz. in Saxifraga stellaris, 

 S. nivalis, and S. cernua, very reduced shoots with small rosettes of foliage-leaves 

 are formed on the terminal branches of the floral axis, or bulb-like buds arise in the 

 axils of the bracts on the upper part of the stalk which, like those of the viviparous 

 Polygonum, send out green foliage-leaves before they fall or become loosened (see 

 figs. 342 ^' ^' ^' *' ^' "■ "■ p. 455). Sedum villosum, which grows on moors, develops 

 short, leafy sprouts with thread-like axis in the axils of the stem-leaves. As soon 

 as the stem begins to wither these sprouts loosen and are carried to a short distance 

 by gusts of wind. They send out delicate I'oots as soon as they find a resting-place 

 and new plants are established. 



A very peculiar mode of detachment and distribution of sprout-like offshoots 

 is found in many species of House -leek {Semperviviirn). The Serapervivum, 

 soboliferuvi illustrated here may be taken as an example. The thick, fleshy leaves 

 of this plant are arranged, as in all House-leeks, like rosettes on abbreviated axes, 

 and the new rosettes are always laid down as minute buds in the axils of the 

 rosette-leaves. From these buds proceed thread-like runners, furnished with small 

 adherent scales, ending in a reduced shoot. The crowded leaves of this reduced 

 shoot enlarge, forming a small rosette, the leaves being folded so closely together 

 that the whole structure has a spherical form. For some time the round rosette is 

 nourished bj^ means of the filamentous runner from the old jjlant, but afterwards 

 the runner withers and dries up and the rosette breaks away from it. It is now 

 quite separated from the parent plant (see fig. 453). A gentle breeze is sufiicient 

 to roll along the small detached balls; and as the House-leeks in question choose 



