PROPAGATION OF PLANTS. 143 
in the Bryophyllum and the Bog Orchis (Malazis paludosa) : 
and, 4. By means of the minute buds or eyes found in the 
tubercles of yarious plants, as the Potato (Solanum tubero- 
sum). 
565. All these buds resemble seeds in this, that when de- 
tached from the parent, and placed in the earth, they pro- 
duce new plants. They differ from seeds, in not being 
formed by sexual organs: in not being able to preserve their 
Vitality for such a length of time; in not having distinct 
_ parts, such as radicle, gemmule, and cotyledons, being mere- 
ly extensions of the substance of the parent; and in always 
producing the same variety. Hence the advantage of pro- 
pagating the potato by buds; we have found a variety well 
adapted for use as an article of food, and we can ensure its 
reproduction. If grown from a seed, a very different variety 
might be produced, which would not have the same nutri- 
_ tious properties. : 
566. Alpine Meadow-grass (Poa alpina), and Viviparous 
_ Alpine Bistort (Polygonum viviparum), frequently bear little 
_ buds in their spikes. All plants which increase by buds or 
_ bulbs produce few seeds, and are called viviparous. 
3. Propagation by Layers and by Slips. 
567. Propagation by layers consists in surrounding a 
_ young branch with moist earth, in which case it throws out 
_ Toots, and very soon becomes an independent plant. It is 
_ customary to make a small incision at the part placed in the 
earth, or to pass a ligature round it. This intercepts the 
descending sap, which, by being accumulated, excites the 
latent germs ; and these, being developed in the earth, be- 
come roots. ey ae 
_ 568. Sometimes the branch is bent downwards and — : ist 
ened in the earth, as in the Vine, which is always propagat- 
ed in this way; and many plants propagate themselves 
naturally in this way, the stems or branches lying on the 
| and taking root where they come intimately into 
tact with it, as the Currant-bush and 
