192 APPLICATION OF PRINCIPLES. 



we see Ferns of many kinds, especially Woodwardia 

 radicans, propagating themselves by offsets from the 

 leaves ; Mr. Turpin tells us that floating fragments 

 of Watercress leaves, cut up by a species of Phryga- 

 nea for its nest, " produce presently from their base, 

 and below the common petiole, at first two or three 

 colourless roots, then in their centre a small conical 

 bud, green, in which are found, or rather from which 

 successively arise, all the aerial parts of a new Water- 

 cress plant, while the roots multiply and lengthen." 

 {Comptes rendus, 1839, sem. 2, 438.) Mr. Flourens 

 also mentions a case of Purslane, whose leaves, 

 divided into three, produced as many new plants, 

 each having a root, stem, and leaves. In the Trans- 

 actions of the Horticultural Society, is an account of 

 a Zamia each of whose scales produced a new plant, 

 when the central part of the stem was decayed. 

 Finally, the following case is named in the same 

 work (vol. V. p. 442,) by Mr. Knight : — 



"In an early part of the summer, some leaves of 

 Mint (Mentha piperita), without any portion of the 

 substance of the stems upon which they had grown, 

 were planted in small pots, and subjected to artificial 

 heat, under glass. They emitted roots, and lived 

 more than twelve months, having assumed nearly the 

 character of the leaves of evergreen trees ; and upon 

 the mould being turned out of the pots, it was found 

 to be t'\ eiywhere surrounded by just such an inter- 

 woven mass of roots as would have been emitted by 

 perfect plants of the same species. These roots pre- 

 sented the usual character of those organs, and con- 



