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POPULAR SCIENCE REVIEW. 
cases the extreme end of the branches was bent, so that from 1 to 9 inches 
was inclined at from 2° or 3° to 5° below the horizon ; but it can hardly be 
imagined that this fact influences the growth of roots at the apex, and 
experiment shows that it is not necessary that even a single inch should be 
inclined below the horizon. A bramble branch was tied apex upwards to a 
vertical stick, and was surrounded by damp moss, and covered with water- 
proof cloth ; imder these circumstances a plentiful crop of roots sprang from 
the terminal part of the branch. This result, combined with observations 
made with brambles growing on a steep bank, shows conclusively that an 
internal impulse or morphological force regulates the growth of roots in the 
bramble. 
When a cutting is made from a bramble, the only growth that takes 
place is the development of the axillary buds at the apical end of the cutting. 
Under certain circumstances these side shoots take on a root-bearing function. 
They are stunted in growth, being perhaps 10- 12 mm. in length, and 3 or 
4 mm. or more in breadth ; they assume a peculiar club-like form, being thicker 
at the apex than at the base, and are clothed with rudimentary scale-like 
leaves, from among which a number of relatively large roots spring forth. 
In order to determine whether the production of this root-bearing type of 
shoot is determined by gravitation, or by a ‘ morphological force,’ cuttings 
were made from branches whose direction of growth was above the horizon. 
Such cuttings were hung apex upwards, and it was found that the most 
apical buds were capable of developing, under these circumstances, into the 
root-bearing type of branch. Similar rooting side-shoots are produced by 
cuttings made from branches which have grown beneath the horizon, and it 
is therefore clear that gravitation is not the determining force in this form 
of root production. When the end of a branch is injured, as often 
occurs when a bramble grows along the ground near a pathway, the most 
apical bud or buds produce branches which take root, instead of the parent 
branch ; either an ordinary branch is produced, which after a certain course 
of time makes roots at its extremity ; or under certain circumstances the 
stunted, club-shaped, root-bearing side shoots may be developed, whose whole 
formation is devoted to the bearing of roots. It is therefore clear that the 
production of such shoots in cuttings is the same process that occurs in 
branches injured in a state of nature — a process which enables the branch 
to perform the function whose normal performance has been interfered 
with. And this fact enables us to see in what way a morphological 
growth-impulse is better fitted for the requirements of the case than any 
possible dependence on gravitation as a guiding force. When the end of the 
branch is injured, it is clear that if a branch is to be developed to carry on 
the function of the injured apex, it will have the best chance of success if it 
starts from the position already gained by the end of the original branch 
before it was injured. Therefore the bud which is nearest to the injured 
apex will be the most suitable one to be developed into a new branch. And 
this is equivalent to saying that the place where the new development is to 
take place is determined morphologically, and not by gravitation. 
Thus in the bramble the behaviour of cuttings is a repetition * of the 
See Vochting, Organbildung , p. 107. 
