THE USE OF SHOOTS FOE PROPAGATING 177 



does not take place (Conifers and Ericas). In these cases it 

 is advisable to cut into the large knots of callus tissue. By 

 this means the cambium layer receives a check, and a greater 

 massing of the plastic substances takes place in the regions 

 above the cut, and thus a stimulus is set up which may often 

 result in the production of roots. 



This method of procedure succeeds in cuttings (often leaf- 

 less) taken from old wood, and has some similarity to the 

 ringing of shoots. In the case of ringed shoots, the tissues 

 forming the upper lip grow out into an expanding mass of 

 cells, which cover in the exposed woody cylinder. If we 

 imagine this woody cylinder to be cut through near the upper 

 end of the ring after the production of this callus mass, and 

 picture the latter covering in the cut surface, then we would 

 have what actually takes place in a woody cutting. 



In the case of shrubs with deciduous leaves, the best time 

 for taking cuttings of woody portions is the beginning of the 

 winter, or, in the case of shoots which will not be damaged by 

 the frost, the latter portion of the winter immediately before the 

 active growth of the spring takes place. Strong slips cut back 

 to three or four eyes should be bound up in bundles and placed 

 in a cellar, or only temporarily covered with soil, and when the 

 spring approaches be planted in rows in a north aspect with 

 only about two eyes projecting from the soil. In this way 

 old wood which has been pruned away in the early spring may 

 be used for cuttings. This at least answers in the case of 

 Bom, Weigelia, Cornus, Beutzm, Zonicera, Bibes, Spirea, &e. 



The callus formation in the case of herbaceous cuttings is 

 somewhat different. Generally more tissues take part in the 

 healing process. It is here especially the pith which forms 

 the bulk of the callus ; the older cortical tissues may, how- 

 ever, be very active. Even the vessels of the wood may take 

 part in this formation of callus {Begonia, Thunbergia), as the 

 cavities of the vessels may become blocked with thylloses, which 

 may grow out over the cut surface. 



Propagation by means of such herbaceous cuttings is the 

 most advantageous means of propagating plants, and this is 

 true of woody plants too ; only the treatment of the cuttings 

 is quite a diiferent one. We must always remember, that 



M 



