12 



ORGANOGRAPHY. 



b. The Offset. (Fig. 212.)— This is a short, prostrate, more or 



Fig. 212. 



Fig. 212. The offset of 

 Scmpervivum. 



less thickened branch, which produces 

 at its apex roots and a tuft of leaves, 

 and thus forms an independent plant, 

 which is capable of producing other 

 offsets. It is seen in the Houseleek. 

 It differs very little from the ordinary 

 runner, except in being shorter and 

 somewliat thicker. 



c. The Stolon. — This is a branch given 

 off above the surface of the ground, 

 but which curves or proceeds down- 

 wards towards it, and when it reaches a moist spot it produces 

 a root and an ascending stem, and being thus capable of ac- 

 Fig. 213. quiring nourishment indepen- 



dently of its parent it ulti- 

 mately forms a new individual. 

 The Currant, Gooseberry, and 

 other plants, multiply in this 

 way. All such plants are said 

 to be stolnniferous. Gardeners 

 imitate this natural formation 

 of new individuals, when they 

 lay down a branch into the 

 earth, from which a new plant 

 is ultimately formed. This 

 process is technically called 

 layeriny {fig. 213). 



d. The Sucker (Figs.2\Aa.na 

 215.) — This is a branch which 

 arises from the stem below the 

 surface of the earth, and which 

 after proceeding in a horizon- 

 tal direction for a certain 

 distance, and giving off roots 

 in its course, turns upwards 

 into the air, and ultimately 

 forms an independent plant, as in the former instances. Plants 

 thus producing suckers are said to be surculose. Good examples 

 of this form of stem are seen in the Rose, the Kasphcrry, the 

 Mint {fig. 215), &c. The sucker can scarcely be said to differ 

 in any essential ])articulars from the stolon, except thar it is 

 originallv subterranean, and ultimately becomes aerial, while the 

 stolon is'first aerial and then subterranean. This form of stem 

 is an illustration of the impossibility of drawing any distinct 

 line of demarcation Ijctween aerial and subterranean stems, as 

 it is both at different parts of its course, and hence might be 

 placed in either division. 



Fig. 213. Plant, showing the process 

 of layering. 



