Vol. XII. Xo. 290. 



THE AGRICULTURAL NEWS. 



183 



PROBLEMS IN PROPAGATION BY 

 CUTTINGS. 



Professor Bayley P.alfour, F. It.S, delivered as the 

 eighth '.Masters Lecture', an e.xtremelj- interesting and prac- 

 tical dissertition on the .subject of propagation by cuttings. 

 The lecture is publl'hed in the Juurnat i,f the Royal Horti- 

 cultural Sucteiij, Vol. XXXVIII, Part 3. 



Professor P>alfour commenced by raising the ijuestion a.s 

 to the truth of the commonly made statement that many 

 plants cannot be propagated by cuttings In the cour.-se of 

 the lecture it is made evident that in the light of modern 

 investigation this statement is unjustified. Two remarkable 

 cases ;ire cited early by way of illustration: one being the 

 case of a species of Gypsophila which was formerly believed 

 to be unresponsive to vegetative propagation, but which had 

 been shown bj- the author to be easily reprodueed by inter- 

 nodal cuttings The second case concerned a plant of great 

 importance in the Tropics — the bamboo — which until recently 

 lad been considered only sexually reproducible. Professor 

 Balfour, however, has shown the bamboo to be readilj' 

 increased by cuttings 



Procreding ne.xt to general con.siderations of the most 

 interesting nature concerning plants as individual organisms, 

 it is pointed out that a plant, unlike one of the higher 

 animals is not, strictly speaking, one individual. It is 

 a colonial organization. 'A plant is conipo-ed of a sheet 

 of protoplasm (living substance) stretched over a skeleton.' 

 A limb of a plant can be lemoved and :nioilier will grow to 

 replace it; if the limb of an animal be removed, only mutil- 

 ation can result. A plant is therefoie potentially immortal. 



Two common instances of vegetative reproduction in 

 nature were next cited — those of the Iris and the strawberry. 

 The former plant creeps along under the soil forming new 

 additions to its body; in fact it is an accident M' the plant 

 does not continue to live for ever In the case of the latter 

 example, thw pknt extends itself by ninpers— by the form- 

 ation of roots near the terminal bud at the end of the 

 prostrate offshoot. 



Consideration of these two cases shows that the 

 necessaiy conditions for reproduction are (a) that the young 

 buds which give ri.=e to the new shoot must receive ample 

 food-supply from the parent plant until it has rooted itself; 

 (b) that there be water to stimulate root development. These 

 two facts are of primary importance. 



After referring to the advantages that accrue to 

 gardeners from the presence of the bulblets, corms and the 

 like amongst monccotyledonous plants, the author proceeded 

 to the important subject of callus formation in relation to 

 vegetative propagation. The growth of callus consists in 

 the formation of a mass of living cells under the stimulus of 

 wounding In an ordinary dicotyledonous stem or root it 

 may take origin in the pith, in the medullary rays, in 

 the cortex, or in the active wood cambium, and it forms 

 lobulated projecting mas.ses at the [joint where it occurs. 

 Callus more rarely forms in monccotyledonous plants — 

 these are content to heal vi^ounds by a cork covering 

 only; when it does appear, however, it arises from the 

 cortex of the stem. Callus formation is a mark of the 

 colonial organization of the plant already referred to. 

 It is associated with the formation of adventitious roots. 



In continuation, the lecturer proceeded to contrast the 

 readiness with which can be propagated cuttings from soft- 

 wooded and hard wooded plants. The difficulty met with in 

 the case of hard,-wooded plants is explained by the fact that 

 the absorption of water is less easily effected than in the 

 case of soft cuttings. For other reasons, which are later 



referred to, resinous planf.s, and those rich in latex may 

 also be difficult subjects for propagation by cuttings. 



After pointing out the nature of the development of 

 a dicotyledonous cutting, the tjuestion as to whether it is- 

 advisable to remove the leaves at the base of a cutting is- 

 referred to. It is pointed out that the practice of leaving 

 them has these advantages; (a) the cutting is saved the 

 healing of the wound caused by their removal; (b) the 

 lower leaves sunk in the soil may root like the stem and aid, 

 thereby, water absorption; (c) the lower leaves will aid in the 

 manufacture of food for the cuttings. Another point 

 considered was the fact that some plants propagate far more 

 readily if the cutting be made through an internode than 

 through a node, and vice versa. As an illustrntion, Clematis 

 cannot be propagated if nodal cuttings are used, wherea."? 

 internodal cuttings may be 'struck' within a fortnight. It is- 

 indicated that an investigation of the causes of .such, 

 ditierences in cuttings is one of the problems of propagation 

 which yet remains to be solved. 



.Alluding again to callus formation, the interesting ancE 

 extremely im[)ortant feature was noted that, however difficult 

 it may be for a cutting to strike, yet once callus is produced, 

 root development can always bestimulated by paringthis callus. 



After referring to the importance of the size of cuttings- 

 illustrated by the fact that small cuttings of hard wood 

 plants germinate quicker than large ones, the lecturer dwelt 

 upon the significance of resin in relation to propagation. 

 When, for insiance, cuttings are taken from coniferous trees, 

 the shoots instead of producihg callus, generally excrete resin 

 This flows out copiously over the surface, covering it- 

 effectively with a hard skin, thereby constituting a hindranet-^ 

 to the exit of young rootlets. It is necessary not only to 

 remove this resin but to check its exudation. This can be^ 

 done by plunging the cut end of the cutting in neacly 

 boiling water. The cut resin canals are thus sealed and 

 doubtless at the same time the heat .stimulus promotes forma- 

 tion of callus. Dicotyledonous plants with resinous and 

 milky juice are in like ca-se with coniferous, and require to b&- 

 treated after the same fa.shion. 



The actual state of a shoot to be used for a cutting was= 

 another point taken for consideration. A vigorou.sly growing; 

 shoot removed from a plant and at once placed in the nidusi 

 for propagation may fail to 'strike'. Its vigour is probably 

 too great The soundness of th" practice of allowing some- 

 cuttings to dry slightly before planting in soil is clearlj'^ 

 supported by this interesting feature of development. 



The subject will be continued in the next issue of the.- 

 Af/riniltiirnl A'ews. 



Peripatus in Tobago. — In the Aijrkdltvral News, 

 Vol. .V, Xo 238, p. 186, a lengthy account will be found olf 

 the genus oi animals designated by the name I^eripatu."^ 

 a family closely related to the insects. Reference to this- 

 article will show that the Peripatus was originally described 

 from the West Indies, by (Juilding in 18"2(), the first speci 

 men having been obtained from the island oi St. Vincent 



Quite recently information has been received from the 

 Smithsonian Institution of the United States National 

 Museum, \Vashingtr:n, to the effect that Mr W K. Broad- 

 way of Tobago, bas just sent an interesting specimen oC 

 Peripatus from Tobago, where these nnimals were not pre- 

 viously known to occur. It is stated by Mr. A. H Clark,, 

 of the above institution, that the specimen represents 

 Peripatus {Epi/Hiripattts) Triuidadeu%is, Stuhlmiinn l-u'; is. 

 probably a recognizable variety for which Mr. Clark is 

 suggesting the name Broadwaji in a paper entitled 'PiccoIe„ 

 Xole sn degli Onychophora' now in press. 



