454 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



some of these plants — for example, species of Abies and Picea — lies in 

 this, that the terminal shoot alone gives a good radially impressed 

 offspring. The dorsiventrality of the lateral shoots is so engrained in 

 the organism that it reappears in the product of a cutting from a 

 lateral shoot. And so propagation by cuttings does not always spell 

 multiplication. Then the fact that the Ooniferae generally do not form 

 callus freely has been advanced as the reason why they are difficult i 

 subjects for vegetative propagation. It is true that pines and firs do 

 not develop stool-shoots, and our records of rooting branches of conifers i 

 are few — fewer than investigation will ultimately support, I believe — 

 but all conifers form some callus. Far more of an obstacle is the j 

 resin. Deficient as they relatively are in the usual means — callus — I 

 which Nature provides for protection of wound-surface, this resin j 

 serves as a substitute or accessory means of protection. When present, n 

 the resin flows out copiously on an injured surface, covering it effec- ' 

 tively with a hard skin. The significance of this in propagation is 

 evident. Over the cut surface of the cutting and any callus formed 

 there the resin hardens and constitutes a hindrance to the exit of 

 young rootlets. What, then, is the propagator to do? Simply scrape 

 off the resin-skin. Most resinous conifers, if treated after this fashion 

 and under the application of the wound-stimulus of paring their callus, 

 strike freely. But this is not the whole story for conifers, like Pinus, \ 

 for example, from which the outflow of resin is copious. This exuda- j 

 tion must be checked, and the simplest process is that of plunging the 

 cut end of the cutting in nearly boiling water. The cut resin canals 

 are thus sealed, and doubtless, at the same time, the heat stimulus 

 promotes formation of callus. (Figs. 162, 163.) 



Dicotylous plants with resinous and milky juice are in like case 

 with conifers, and require to be treated after the same fashion. 



The actual state of the shoot about to be. used for a cutting requires 

 attention in some cases. A vigorously growing shoot taken off a plant 

 and at once placed in the nidus for propagation may fail to strike. Its 

 vigour is too great. The food-material in the cutting is really required j 

 for the callus healing at its base. If the claims of the apex are so 

 great as to deflect the food-supply, as may well be in the case I have 

 mentioned, callus-formation and root -formation may be so delayed as 

 not to forestall wilting. The soundness of the practice O'f allowing 

 some cuttings to dry slightly before planting in soil is supported by 

 this. 



An interesting problem of propagation by cuttings is offered by 

 monocotylous plants. They exhibit some striking features in which 

 they differ from dicotylous plants, and I am disposed to think that the j 

 difference I am about tO' describe may be one of the reasons for the 

 prevalent idea that some of these monocotyls do not propagate by 

 cuttings. 



In illustration, take the case of Asparagus or like plant (fig. 164). 

 Here, as in monocotyls generally, a short terminal portion of the shoot 

 will give no result as a cutting. A larger branched twig must be severed 



