April 30, 1888.] 



SCIENTIFIC NEWS. 



375 



The members of the Conference were of opinion that 

 it would be very advantageous for senders of letters and 

 telegrams to adopt the civil Greenwich day as the 

 universal day, because its commencement falls in the 

 hours of the night throughout Europe, Africa, and Asia. 

 In the United States and Canada the change of date 

 would occur after four o'clock in the afternoon, and in 

 Australia before ten o'clock in the forenoon. In fact, the 

 day would not commence in any important place during 

 ordinary office hours (10 a.m. to 4 p.m.), except in New 

 Zealand. The letters a.m. and p.m. would be omitted 

 in telegrams ; this would save the expense of transmis- 

 sion, which is a considerable item in international 

 messages, for in the Western Union Telegraph Company 

 alone no fewer than 150 million letters annually would 

 thus be saved. Besides, the chances of error in trans- 

 mission of dates would be very much lessened. 



It is, however, curious to notice the alteration which 

 the new system will occasion in the ordinary time associa- 

 tions. The hours of sleep, work, and meals will be changed 

 in every place once for all. Instead of continually trans- 

 lating the universal time into the customary local time, 

 men would once for all translate the ordinary time into 

 the universal time. In the Eastern States of North 

 America, business men would indicate midnight by 

 5 h. U.D. Instead of rising at 8 o'clock a.m. a man 

 would rise at 13 h. U.D. His time for work in the 

 office would be represented by 15 to 21 instead of from 

 10 a.m. to 4 p.m. He would dine at 23I instead of half- 

 past 6 p.m. But soon the little inconvenience would 

 pass away, just as one soon gets accustomed to the 

 change of coinage in a foreign country. 



It is gratifying to observe that in the United States 

 the railway managers, representing 60,000 miles of 

 railway (98 per cent, of the whole), have agreed to the 

 employment of the universal day. The Americans 

 have prejudices, but they know when to renounce them, 

 and the advantage to them in business by the alteration 

 will compensate for the temporary feeling of having to 

 yield to Great Britain in the fixing of the arrangement. 



■>-5»<^i<^5<f-» 



THE FORMATION AND FUNCTIONS OF 

 STOMATES.— III. 



(^Continued from page 353.) 



THE question of the value of transpiration to the plant 

 has given rise to much discussion, but there can be 

 very little doubt that it lies chiefly in the keeping up of 

 constant currents of sap in the woody tissues of plants, 

 carrying with it in solution (all plant-food must be either 

 liquid or gaseous) earth-salts — phosphates, nitrates and 

 sulphates — that these substances may be brought into 

 the leaf at a time when the most elementary form of 

 plant-food, viz., starch, is being formed. As before 

 stated it is in the leaves that the bulk of nutriment is 

 manufactured, and as land-plants are not constructed to 

 obtain their food in its elementary state like submerged 

 aquatic plants, by mere osmosis, thevaluable inorganic mat- 

 ters from the soil could never be brought into the leaves 

 in sufficient quantity to properly nourish the plant if it 

 were not for transpiration. 



Proof that transpiration is necessary lies in the fact 

 that when it is hindered by growing large plants in a 

 very damp atmosphere they never show a healthy 

 development. Certain species of the cactus and of the 



stonecrop order iCrassitlacece) exhibit little vigour of 

 growth because devoid of a large area of green surface. 

 The need lor absorption and evaporation of such a 

 considerable quantity of water will be at once seen when 

 it is known that the proportion of dissolved salts to 

 water is i to 2,000 or even less, so that in order to 

 obtain one ounce (Troy) of earth-salts a plant has to pass 

 through its system about 166 lbs. of water. The supply 

 of these earth-salts is regulated by the rate of the 

 ascending currents, which in part is influenced by the 

 simple but important physical fact that watery vapour 

 passes off less readily from a saline solution than from 

 pure water, and also probably from its greater density, 

 rendering absorption slower. It is for this reason that 

 plants grown in strongly manured soil transpire less than 

 plants grown in poor soil. The importance of this 

 regulation of the currents lies in the fact when the soil is 

 poor in earth-salts more water is carried up to make up 

 the deficiency ; and when the soil is very rich the cur- 

 rents move more slowly so as not to overgorge the plant 

 with more food-materials than it can make use of, a condi- 

 tion which would most likely hinder the internal work of 

 the plant in building up its tissues. In addition to the 

 density of the solution passing up the plant, there are 

 other causes which materially influence transpiration. An 

 instance is given above of the effect of a damp condition 

 of the outer air in checking it, and consequently the 

 slowness of transpiration when other circumstances are 

 favourable is in proportion to the moisture in the atmo- 

 sphere, but complete stoppage until the atmosphere is 

 quite saturated and its temperature as high as that of 

 the leaves. In spite of the large quantity of water 

 required by land-plants for transpiration it is a notable 

 fact that they grow best in soils which are not always 

 very damp, but which become saturated occasionally. 

 This is borne out by one of the commonest rules in 

 cultivating plants that too much water must not be 

 supplied to the roots for fear of rotting them. It is from 

 May to September, when the soil is in its driest condition, 

 that most transpiration is going on. During the winter 

 it entirely ceases in most plants. 



Returning once more to the apparatus by which this 

 important work of transpiration is effected — the stomates 

 — it may be well to conclude with a few particulars 

 relating to their position, form, and size. As has been 

 stated they are found chiefly on the under-surface of 

 leaves, but they are also found on their upper surface, 

 though not in such numbers, as instance the leaf of the 

 white lily, which has from 20,000 to 60,000 per square 

 inch on its lower surface, and only 3,000 per square inch 

 on its upper surface. In plants the leaves of which have 

 both surfaces alike, viz., those which assume a vertical or 

 edgewise position, as the iris, they number the same on 

 either side. In others, such as the water lily, which 

 have floating leaves, they are wholly on the upper 

 side. Up to the present the stomates have been 

 spoken of in connection with leaves and stems, but they 

 are also present on other parts, though in very limited 

 numbers, such as the petals of flowers and even the 

 interior parts of the fruit and seeds, as in the wallflower 

 and walnut, and on underground stems and leaves. 

 They are very seldom to be found on the skin of true 

 roots, on that of etiolated plants, or on those which have 

 been blanched by growing in the dark, or on leaf-ribs. 

 Their infrequency on submerged plants has been men- 

 tioned, but when these are grown in air they produce- 

 stomata like land-plants. Their shape is generally oval,. 



