NEW FORMATION OF ORGANS IN REGENERATION 45 



base ; frequently these are roots only, but in other cases the primordia of 

 shoots appear as well, and there are not a few plants, such for example 

 as Begonia, which are increased by leaf-cuttings. We can best bring 

 these facts together under one general point of view if we assume with 

 Sachs that the material which is devoted to the formation of the different 

 organs is different. In the normal life of plants shoot-forming material 

 would flow towards the vegetative points of the shoot, and root-forming 

 material would pass to the root-system, and therefore, if there should be 

 an interruption in the path of the stream, roots would of course appear at 

 a root-pole and shoots at a shoot-pole, whilst in the leaves, seeing that 

 the direction of the current of plastic material is always towards the 

 shoot-axis, the new formations naturally appear at the base. Gardeners 

 take care when they place the severed leaves of Begonia in moist sand 

 to snick the thicker leaf-ribs, and then above each cut a bud 

 appears. 



The influence of gravity and light upon the phenomena of regenera- 

 tion will be referred to in the Fifth Section. Here I will only further 

 refer to one case which in a specially interesting way confirms the view 

 that the place for the formation of new organs in regeneration is definite, 

 and is primarily dependent upon the direction in which the plastic sub- 

 stance moves in the uninjured plant. 



Many monocotyledonous plants seldom or never set seed because 

 their vegetative propagative organs, for instance bulbs and corms under 

 ground, exercise a stronger attraction upon the plastic material than do 

 the ovules after fertilization has taken place l . We have examples of this 

 in Lilium candidum, Lachenalia, and others. On flower-scapes of Lache- 

 nalia luteola 2 , which have been severed from the parent plant, bulbils 

 arise near the base, because the current of plastic material was directed 

 towards the base. In Hyacinthus orientalis, on the other hand, bulbils 

 arise at the apex of severed flower-scapes and the seeds ripen normally 

 because the current of plastic material flows to the ovules in which 

 fertilization has taken place. The cause of the difference is not, as 

 Vochting has asserted, to be found in the limited or the unlimited 

 growth. 



The capacity of plants for artificial multiplication by cuttings is also 

 related to the phenomena just briefly described. Different species behave 

 differently in this respect ; many are not able to produce new roots on 

 detached twigs, and one and the same plant may even behave differently 

 at different ages. The juvenile form of the Cupressineae, for example, 

 roots very easily, the twigs of the older plants do so with difficulty. In 



1 See the Fifth Section. 



3 H. Lindemuth, Uber Bildung von Bulbillen am Bliitenschafte von Lachenalia luteola, Jacq., und 

 Hyacinthus orientalis, Linn., in Ber. der cleutsch. botan. Gesellsch., xiv. p. 247. 



