March 27, 1889.] 



Garden and Forest. 



153 



on strong, vigorous shoots they are not infrequently furnished 

 with two or three spiny teeth. The drooping raceme is longer 

 than the leaves, is either simple or compound, and is often 

 corymbose ; the berries are elongated in form, violet in color, 

 and are furnished with a conspicuous style and capitate 

 stigma. 



In the districts where it is found wild, Royle says J3. Lycium 

 is largely used in the manufacture of rusot. The following lines 

 respecting rusot ^xq copied from Royle: "The wood and 

 bark of the Himalayan species of Barberry are not only used 

 simply in India, but an extract is prepared from them which is 

 to be found in every bazaar, and described in all the works 

 on materia medica. This is prepared by digesting in water 

 sliced pieces of the root, stem and branches of any of the 

 species of Barberry In an iron vessel, boiling for some time, 

 straining and then evaporating to a proper consistence. This 

 extract is much employed in Indian medicine, and every- 

 where known by the name of rusot." George Nicholson. 



Royal Gardens, Kew. 



Principles of Physiological Botany, as Applied to 

 Horticulture and Forestry. 



XIII. — Some of the Conditions Which Favor Rapid Growth — 

 Certain Physical Phenomena of Growth. 



THE Measurement of Growth is by no means so easy a 

 matter as would appear at first to a casual observer. In 

 the case of strong shoots, which increase in length very rap- 

 idly, it is, of course, sufficient merely to make measurements 

 with any accurate scale, at proper intervals. For instance, 

 shoots of Bamboo can grow at the rate of six inches to one 

 foot in twenty-four hours, and such rapid growth can be very 

 readily measured. But when we are dealing with plants which 

 grow slowly, or when we desire to note the amount of growth 

 during short periods of time, it is necessary to make use of 

 apparatus by which all growth can be registered, and the exact 

 times of growth known. In general, such pieces of apparatus 

 consist of a drum made to revolve regularly, by means of 

 clock-work, and bearing smoked paper, which can be marked 

 by an index connected with the growing part of the plant under 

 observation. When such an apparatus is properly adjusted it 

 can run along for many days, making an accurate record of all 

 the varying rates of growth, and the times of these variations 

 can, of course, be easily compared with the rates. It has been 

 urged that, in the case of such experiments, the plants are 

 withdrawn from their natural conditions and subjected to 

 special conditions in the laboratory which may disturb in many 

 ways their natural activities ; and hence, it is said, it is not 

 right to conclude from these experiments that the growth 

 registered by the apparatus is the same which the plant would 

 have made in the open air or in its natural home. Such objec- 

 tions are not well founded. Nevertheless, they must, in some 

 instances, be taken into account, and, further, it must be re- 

 membered, in examining the general conclusions drawn from 

 the results of experiments of this character, that different 

 plants, under precisely the same conditions, inay behave very 

 differently. In fact, there are a good inany peculiarities or 

 idiosyncrasies of plants which are as yet wholly unaccounted 

 for. But the general statements which now follow are based 

 on an examination of a large number of plants, and doubtless 

 apply, with very few exceptions, to all of the common plants 

 which fall within the province of the horticulturist and the 

 forester. 



Relations of Growth to Temperature. — There appears to 

 be a certain degree of temperature which is suited to the most 

 rapid growth of every plant. Growth can take place at tem- 

 peratures far above this, and can continue at temperatures far 

 below it, but at the optimum the multiplication and the enlarge- 

 ment of cells proceeds most rapidly and uninterruptedly. The 

 degrees which have been iTiade out for some of our common 

 plants are given in the following tal)le : 



Minimum. Maximum. Optimum. 



Wheat, .... 41° F. 108° F. 84° F. 



Cress, .... 34° F. 98° F. 80° F. 



Red Clover, . . 42° F. 82° F. 70° F. 



Indian Corn, . . 48° F. 115° F. 90° F. 



These figures are fair averages of those given by observers. 

 Relations of Growth to Light. — In general it must be 

 admitted that cell-growth is retarded by light. At first this 

 seems very strange when we reflect that it is through the 

 agency of light that the green parts of plants construct all their 

 building materials. The putting of these materials in place is, 

 however, quite a different matter. It can go on in the light, 

 but it proceeds, as a rule, faster in the dark. A inoment's con- 

 sideration will show that all growth of ordinary roots takes 

 place in the dark, and the thickening layers of stems are com- 



pletely shielded from the light ; moreover, the unfolding of 

 buds at the covered growing points of stems and branches is 

 another case in point. To the cultivator of plants the fact is 

 familiar that in a dim light the seedlings are apt to be "drawn," 

 whereas in bright light they are more "stocky," and are better 

 able to resist attacks of disease. The growth is less rapid in 

 the latter than in the former case. Hence we must bear in 

 mind the fact that rapid growth is not by any means neces- 

 sarily that rate which is best for the plant under cultivation. 



Relations of Growth to the Mineral Matters in the 

 Soil. — This subject is one of surpassing importance, since it 

 underlies all success in cultivation. The experiments in this 

 field of observation have been conducted not only in special 

 soils prepared for the purpose, but also by a method capable 

 of yielding even more satisfactory and exact results — namely, 

 by what is known as "water-culture." When seedlings have 

 thrust out one or two strong roots, and a few leaves, they are 

 placed above the surface of the solution which is to be 

 employed in the experiment, and the roots are permitted to 

 dip into the liquid. For instance, one plant will be grown with 

 pure water, another with water containing one of the salts of 

 potash, another with another salt of the same base, and so on. 

 It is plain that such observations can be indefinitely extended 

 to all classes of substances. 



From the myriads of results which have been obtained by 

 this mode of experimenting, the following general conclusions 

 appear at the present time to be justified : 



Growth and the preparation of materials for growth are 

 checked when the substances mentioned below are absent, or 

 are present in too small amount — combinations of potassium, 

 magnesium, calcium, nitrogen, iron, phosphorus. These, to- 

 gether with sulphur in very small amount, and for some 

 plants, sodium and chlorine, may be regarded as absolutely 

 indispensable. Acting on the hints afforded by water-culture, 

 it is possible to provide for a certain species of plant the pre- 

 cise amount of the substances best adapted to the needs of its 

 growth. In practice, however, there are several serious diffi- 

 culties which stand in the way of transferring these results 

 from the laboratory to the garden or the forest. The most 

 perplexing hindrance is that as soon as a solution of these min- 

 eral matters comes in contact with the soil it is liable to under- 

 go changes in composition. Some kinds of soil, notably 

 clayey soils, have the extraordinary power of withdrawing 

 from solutions certain of the matters held in solution, and in 

 this mechanical adhesion, as it is called, the abstracted sub- 

 stances are liable to be acted on by the air which is entangled 

 in the soil. Although the plants may get at these matters after 

 a time, and perhaps in the very best form in which they can 

 use them, we are not sure that what we place on the soil is 

 what the plants are going to get. For exact information in 

 regard to this most important matter the reader may consult 

 some authoritative work like that which is mentioned at the 

 end of this paper.* 



Physical Phenomena of Growth. — The pressure which is 

 exerted by a growing part is in some cases, capable of meas- 

 urement. The results of such measurements are surprising. 

 Only a few examples can be cited here ; other cases may be 

 found in the treatises referred to in earlier papers of this series. 



Darwin found that the tiny underground stemlet of a germi- 

 nating bean was able to move a weight of rather more than 

 three pounds, and in another instance about eight pounds. 



In the case of the fruit of a squash placed in a frame-work 

 connected with a lever, a force of more than two tons was 

 exerted by the multiplying and enlarging cells. 



When trees grow on ledges the increase in the thickness of 

 the large roots at their very base will frequently raise the whole 

 trunk for a distance of an inch or more, the firm ledge under 

 it affording an unyielding support, against which the pressure 

 of the cells of the thickening roots comes. This fact should be 

 borne in mind in the examination of those cases of supposed 

 growth in height of old thick stems which may have served as 

 gate-posts. By the raising of the end of the gate above its 

 former level the old stem, which we know is incapable of 

 growth in length, may appear to have grown, whereas it was 

 simply being lifted by the roots underneath, f 



Cases in which growing roots have torn asunder stone foun- 

 dations, into the crevices of which they have insinuated them- 

 selves, are doubtless familiar to all the readers of this paper. 

 The force exerted in all these instances has been exercised 

 solely by the innumerable delicate, thin-walled cells, which 

 increase in number and in size in the orderly manner we have 

 attempted to describe. 

 Cambi-idge, Mass. George Lincoln Goodale. 



* Slorer's Agriculture. 



tSee also Garden and Forest, March 6, page 109. 



