254 



HARDWICKE'S SCIENCE-GOSSIP. 



.pointed end are unnecessary. I leave the cigar smoker 

 to meditate thereon while this end is between his 

 lips, merely adding that my own reflections suggest 

 the desirability of an amber mouthpiece. 



In my own house I insist upon the washing of all 

 fruit that is eaten in its raw state, and suspect that 

 ]jlums have been falsely accused — as plums — of 

 propagating cholera. Most of them in our markets 

 are imported from the South, after much handling 

 •by dirty people. This is also the case with figs, 

 dates, and raisins. Fortunately for us, the dried 

 dwarf grapes of Greece ("currants") are usually 

 washed by dealers to improve their appearance, and 

 are cooked. Those who have travelled in the 

 interior of Greece will understand why I mention 

 these with special emphasis. 



A communication from B. Sc, in the September 

 number of Science-Gossip, page 212, reminds me 

 of some experiments I made many years ago in 

 mounting microscopic objects. I bought specimens 

 of all the gums and gum resins commercially obtain- 

 able,- treated them with various solvents, for the 

 purpose of obtaining a substitute for Canada balsam, 

 something that should hold down the thin glass 

 cover, envelope and hermetrically seal organic 

 preparations, especially sections, and yet be suffi- 

 ciently limpid when in solution to permit the free 

 removal of air bubbles, which as all microscopists 

 ];now, are so obstinately retained by the viscosity 

 of Canada balsam. I succeeded, as usual, in 

 securing a large crop of failures, but obtained one 

 success by dissolving gum Thus (the basis of frank- 

 incense, a resin of the " arbor thurifera " or thuja) in 

 bisulphide of carbon. I found that this solution is 

 very limpid and transparent, and rapidly solidifies. 

 The vegetable sections that I mounted stood well, 

 but having almost forsaken the microscope, I had 

 nearly forgotten it. Probably some of the readers of 

 Science-Gossip who are faithful to microscopic 

 work will try it, and report results in SciENCE- 

 GossiP for the benefit of brother amateurs. 



The drosera controversy has not by any means 

 subsided. Darwin, Kellermann, Raumer and Rees, 

 contend that the insects capturetl serve as food, that 

 these plants are truly carnivorous ; while Regel and 

 others deny this. H. Biisgen in a recent paper, of 

 which an abstract is published in the September 

 number of the Journal of the Chemical Society, 

 attributes the different conclusions to the varying 

 conditions under which the experiments were made, 

 with plants possibly in different stages of develop- 

 ment. The comparison should commence with the 

 weighing of the seeds, and finish with the estimation 

 of the total dry matter of llie plant. 



As the seeds of the Drosera jviuiuli/olia are so very 

 minute, Biisgen commenced with the seedlings. The 

 comparisons were made between plants growing in 

 similar soil — peat previously boiled in a nutritive 

 solution and placed in saucers covered with bell- 



glasses ; one set fed witli lice from vine leaves, the 

 other without animal food. The unfed plants were 

 less strong and healthy than the others ; the fed 

 plants had seventeen flower branches on fourteen 

 plants against nine buds- on sixteen unfed ; and 

 ninety seed capsules on fourteen plants against twenty 

 on the sixteen ; the total dry weight of the fed 

 plants was o"352 gramme against o'lig of the 

 unfed. Other trials gave similar results. 



Cut flowers wither more slowly than leaf twigs 

 from the same plant. This is due to a greater trans- 

 piration from the leaves than from the flowers. If 

 the transpiration of the leaves is arrested the flower 

 will remain fresh for a much longer time than if the 

 leaves are allowed to remain. In like manner the 

 terminal leaf bud lasts longer on cut twigs if all the 

 other leaves are removed. 



Some interesting researches on the self-purification 

 of rivers have been recently made by F. Hulwa. He 

 finds that the water of the Oder on entering the city 

 of Breslau, although slightly contaminated, yielded 

 an excellent drinking-water when filtered. In the 

 course of its progress through the city it showed con- 

 tinuously increasing pollution, the maximum at its 

 exit. A short distance lower down, the self-purifi- 

 cation of the river by the combined action of the 

 oxygen of the air and of vegetable and animal life 

 became very marked, impurities diminishing so 

 rapidly that at a distance of 8f miles from the city 

 the water was in about the same condition as when 

 it entered the city, neither chemical nor microscopic 

 tests showing serious impurity. Complaints have 

 been made against the penny steamboats on the 

 Thames, because they disturb the bottom. So far 

 as the bridges are concerned they may be mis- 

 chievous, but this mischief is not difficult to repair 

 and prevent by the simple device of surrounding 

 the foundations of the threatened arches with heavy 

 .stones, or fundamentally improving the foundations. 

 From a sanitary point of view we may regard 

 these and other steamboats (including even the much 

 abused steam launches) as valuable agents, seeing 

 that agitation of water polluted with sewage is 

 the most effectual moile of purification. The steam 

 tugs on canals which are otherwise stagnant are 

 great benefactors. 



The action of frost upon plants has been recently 

 studied by H. R. Goppert {Annales Agrottomiques, 

 vol. X. p. 41). It had been previously stated that 

 plants, bulbs and roots are killed by sudden thawing, 

 not by the preceding freezing. Goppert submitted 

 potatoes, and the bulbs of hyacinths, narcissus, &c., 

 to a temperature of about 3 degrees below freezing 

 (-1-4° Centigrade) and then suddenly to 15 degrees 

 ( — 8° C.) below freezing. This killed all the bulbs, 

 whether they were afterwards thawed either slowly 

 or rapidly, but none of the bulbs cooled to— I "4° C. 

 were damaged, the potatoes only being frozen. 

 Flowers of the exotic orchids Pajus and Calanthe 



