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SCIENTIFIC NEWS. 



[Nov. 1 6, 1888. 



they are suspended between the horns of goats. Two 

 other species of rhubarb are known in commerce — those 

 of China and Persia. But there are upwards of a dozen 

 species of Rheum which might yield the medicinal pro- 

 duct, and it is remarkable that up to the last century no 

 one knew exactly which species was preferable. 



Boerhaave made some important experiments on this 

 subject. He procured the seeds of various species of 

 Rheum, and sought out the one whose roots resembled 

 most nearly the kind employed in medicine. It is now 

 established that this kind is the Rheum officinale, a native 

 of Eastern Thibet and Western China. It is a herbaceous 

 plant, with strong branching roots and large, broad, 

 palmated leaves, green above and whitish below. The 

 flowers are produced in terminal pannicles of a yellowish 

 white. The aerial stems, and not the roots, of the plant 

 yield the true Chinese rhubard. 



According to Dr. Thorel, the genuine rhubarb is found 

 chiefly among the high mountains of Thibet. The plant 

 grows vigorously only on the borders of the snow-line, at 

 altitudes of about 12,000 to 13,000 ft. The Lamas, per- 

 ceiving the considerable profit to be derived from the 

 trade in this plant, endeavour to seize possession of it. 

 They declare that the root has a sacred character. The 

 harvest is conducted with very peculiar ceremonies, and 

 it concludes with terrible imprecations against all who 

 trespass on the sacred ground until the next harvest. 

 But it appears that, in spite of these solemn prohibitions, 

 both Thibetans and Chinese plunder the forests, caring 

 little for the imprecations of the Grand Lama. 



In 1867 the Paris Societe d'Acclimatation received from 

 Thibet a chest containing roots of the precious plant. It 

 has since been cultivated, and has been the subject of 

 interesting observations, but its medicinal properties are 

 enfeebled in our climates. 



It might be an interesting experiment to try the culti- 

 vation of the medicinal rhubarb in the higher regions of 

 the Alps or the Pyrenees. 



The Rheum hybridum is largely cultivated as an article 

 of food in Britain and in the United States, bearing in the 

 latter country the name of " pie-plant." Cosmos asserts 

 that the early leaves, mixed with a little sorrel to 

 heighten the flavour, are used as a vegetable, and are 

 considered equal to spinach. 



We have only heard of one instance of rhubarb-leaves 

 being eaten in England. A family had been beguiled by 

 an indiscreet newspaper paragraph into trying this 

 spring vegetable. The results were serious, as the 

 leaves of rhubarb contain oxalic acid ! 



The writer goes on to say that the leaves are utilised 

 in this manner during the months of April and May, 

 whilst after May they are used as a material for tarts. 

 He also ventures to assert that such tarts have a finer 

 flavour than that of the green gooseberries so much ad- 

 mired in Northern France, Belgium, and England. 



Every one knows that the flavour of rhubarb is coarser 

 than that of green gooseberries, and that it quickly dis- 

 appears from the markets and shops after the latter 

 have come into season. 



The leaves of rhubarb, which are not eaten, may, it is 

 said, be boiled with potatoes and bran and given to pigs. 



We may add here a brief notice of the other uses to 

 which the rhubarb plant may be turned. In the 

 manufacturing districts of the North, where rhubarb is 

 cultivated on a larger scale than in any other part of 

 England, the leaves are sometimes used in setting 

 indigo vats for woollen dyeing, as an aid to fermenta- 



tion. For this purpose the leaves are collected together, 

 pressed, and used under the name of woad. It must be 

 remembered that in modern days the true woad is not 

 used on account of the trifling amount of indigotine which 

 it develops, but merely as an aid to fermentation. 

 Many experienced and successful blue dyers would not 

 know whether they were employing woad or rhubarb- 

 leaves. 



A less legitimate use for these leaves is said to take 

 place in the manufacture of tobacco. 



Had it not been for the triumphant introduction of the 

 coal-tar colours, the root of rhubarb would have been 

 extensively used in the manufacture of dyes. By treat- 

 ment with nitric acid it may be made to yield fine rose, 

 crimson, purple, and brown shades. But as these dyes 

 were unable to compete with the coal-tar colours, either 

 in beauty or in price, they have fallen into complete 

 forgetfulness. 



The Influence of Sunlight on Trees. — In the 

 latest report of the head of the Forestry Department ot 

 the United States reference is made to the effect of light 

 on the growth of various trees. It is well known, says 

 Professor Fernow, that light is necessary for the develop- 

 ment of chlorophyll, and, therefore, for the life of all 

 green plants, and especially for that of trees. The heat 

 alone which accompanies the light is not sufficient, 

 although the relative influence of the light and the heal 

 on the growth is still an open question, as well as the 

 relative requirements in light of different species of 

 trees. In the case of forest weeds, which in forestry 

 serve as an indication of the amount of shade which the 

 trees exert, and with that their capacity of impeding 

 evaporation, some require full sunlight for their develop- 

 ment, others are averse to a high degree of light. To 

 this must be due the change in the plants of a district 

 when its forests are removed. Then the amount of light 

 or shade needed is modified by site. Where the sun- 

 light is strong, in higher altitudes, drier climates, or 

 where the growing season is longer, or there are more 

 sunny days, some species will endure more shade. The 

 flora of high altitudes in general requires light. Trees 

 nearly always develop best, in other words make most 

 wood, in the full enjoyment of light, but their capacity ot 

 developing under shade varies greatly. The yew will 

 thrive in the densest shade, while a few years overtop- 

 ping kills the larch ; the beech will grow with consider- 

 able energy under partial shade, where the oak would 

 only just keep alive and the birch would die. When 

 planted in moist places, all species are less sensitive to 

 the withdrawal of light. In the open, maples, elms, syca- 

 mores, and others grow well and make good shade trees, 

 in a dense forest they thin out and have but scanty foli- 

 age. Conifers, such as spruces and firs, which preserve 

 the foliage of several years, have perhaps the greatest 

 capacity of growing under shade, and preserving their 

 foliage in spite of the withdrawal of light. In America 

 sufficient data to group the forest trees according to the 

 amount of light required by them have not yet been 

 collected, but rules based on experience have long been 

 formed in Germany, where the behaviour of trees under 

 different conditions of light has been carefully studied. 

 It has been found, for instance, that on the same branch 

 those leaves which are developed under the full influence 

 of sunlight are not only larger and often tougher in tex- 

 ture, and thicker, but that they have a larger number ot 

 stomata or breathing pores than those less exposed to 



