822 



THE DISTRIBUTION OF SPECIES BY OFFSHOOTS. 



shallow depression on the upper side of the thick leaf, and possesses 2-3 leaflets 

 about "5 mm. in diameter (fig. 454^). In the axils of the lower foliage-leaves short 

 sprouts are formed, whose axes are furnished with fairly large crowded rosette- 

 shaped leaves (fig. 454^). In the axils of the lowest arise rudimentary sprouts, 

 with an elongated thread-like axis bearing 8-14 thickly-crowded leaflets at its end 

 (flg. 454*). As soon as the stem carrying the flowers begins to wither, the foliage- 

 leaves and the buds or sprouts in their axils loosen from it and fall to the ground. 

 The succulent, very turgid, almost hemispherical leaves are comparatively heavy, 

 and if the spot where they first fall is sloping they do not lie still, but roll down 



until they are caught by some pro- 

 jecting ledge, or a mossy cushion, 

 or arrive on level ground. Since 

 they carry with them the buds and 

 sprouts formed in their axils, they 

 to a certain extent function as a 

 means of transport. As soon as the 

 offshoots come to rest, they develop 

 rootlets at their base at the expense 

 of the reserve materials of the de- 

 tached succulent leaf. Rootlets are 

 often formed even while the leaves 

 are still adhering to the decaying 

 stem. It is worthy of note that 

 the aqueous tissue of the fallen 

 leaves also plays a part in the 

 establishment of these offshoots. If 

 the spot where they have come to 

 rest is exceptionally dry, as is 

 usually the case in places where 

 Sedum dasyphyllum grows, the 

 supporting leaf may for a long time provide the water necessary for the mainten- 

 ance of the offshoot, and so protect it from perishing. 



The formation of sprout-like offshoots is very remarkable in the Kleinias, 

 natives of the Cape, which belong to the Compositse. Some species of this genus, 

 viz. Kleinia neriifolia and K. articulata, remind one very much in their appear- 

 ance of certain Cacti. The fleshy, much-thickened cylindrical branches are connected 

 with one another by thin strands, and the whole plant looks as if it had been 

 constricted at intervals by ligatures. The strands joining the heavy cylindrical 

 branches break at the slightest pressure, and the upper shoots especially may be 

 broken off" even by a violent gust of wind. The result of the fracture at the constricted 

 places, however, is that the branches fall to the ground. If the plant grows on a 

 slope, the fallen cylindrical shoots roll down until they are stopped by a projecting 

 stone or some other obstacle. When they come to rest they develop numerous roots 



Fig. 454. — The formation of offshoots in Sedum dasyphyllum. 



1 Entire plant ; nat. size. 2^ s, and *, Offshoots which have developed 

 at different levels on the stem in the axils of the leaves. 6 Off- 

 shoots from the floral region. 



