HARDWICKE'S SGIENC E-G O SSIF. 



63 



between the boulders, into the moist soil beneath. 

 Thus it is evident that even more here than amongst 

 the ferns, large bodies of soil are indispensable, and 

 every portion on the surface connected with the 

 whole mass. The principles enunciated for con- 

 structing rockwork above will hold good here. Let 

 the stones or burrs be of a good size ; and, for the 

 sake of good taste, avoid the use of such additions 

 as artificial adornments — shells, or such-like. 

 Whilst recommending a position exposed to the 

 full sun, we do not say that rockeries cannot suc- 

 ceed in half-shaded ones ; on the contrary, whilst, 

 as a general rule, the foregoing remarks are correct 

 for true Alpines, plants can be found in abundance 

 to furnish rockwork in any position whatever. A 

 good use for many of the stronger-growing kinds is 

 as borders to shrubberies [see fig. 46J. The soil 

 for the great bulk of Alpine and rock plants should 

 be sandy loam and grit. There are some species 

 which require peat, but these form a separate sec- 

 tion, and should be cultivated together. The first- 

 named soil is that most generally requisite, and 

 suits all the lai-ge families of Sedums, Saxifrages, 

 Sempervivums, and many other species of great 

 beauty and easy culture." 



MICROSCOPY. 



Dark Lines in Eield op View, — I have a 

 large binocular microscope whose eye-pieces are 

 If inch diameter, by which instrument'! can view 

 objects perfectly stereoscopically with the o, 2, and 

 1-inch objectives, and get an equally illuminated 

 field of view in each eye-piece ; but when 1 use the 

 binocular with a :|^-iuch objective of S0°, I get a dark 

 line across the field, and, on looking into each eye- 

 piece separately, I find them only half-illuminated, 

 viz. the inner half, the outer half of each being 

 perfectly dark. Will some correspondent kindly 

 say if this ought to be, or whether I ought to get 

 each field wholly illuminated when using so high a 

 power? My objectives are all English make. I 

 have no power between the 1-incli and i-inch, so 

 cannot say how the instrument would behave with 

 such.— (?. W. 



Pollen of Petasites fragkans.— Though 

 this is not a British plant, as it was originally intro- 

 duced to England from Italy in ISOG, it is doubtful 

 whether any of our indigenous species abound so 

 much and so early in pollen as P.fragrans, or Sweet- 

 scented Butterbur. It grows rampant at Canter- 

 bury in deserted gardens, where this Butterbur 

 has been profusely in bloom from Christmas up to 

 the present date (Jan. 13). And the pollen-grains 

 are so remarkably beautiful as to afford very delight- 

 ful microscopic objects even at this dreary season. 

 Each pollen-grain is oval, having a length of j J^ of 



an inch, and a breadth of 7^0 ; muricated on the 

 surface, like those of so many other composilai ; 

 becoming globular or sub-triangular, with three 

 scars appearing for the passage of the future 

 pollen-tubes, when treated with diluted sulphuric 

 acid. The pollen-grains are so large that they may 

 be very easily examined under an object-glass of 

 half an inch focus. — Q. F. 



Mounting in Soft Balsam.— Mr. E. Kitton, 

 in the December Gossip, regrets that directions 

 should stiU require to be given for mounting in soft 

 balsam, and, whilst I cannot but equally regret that 

 the beginner in mounting should fiud himself, con- 

 fronted with an array of spring clips, spirit-lamps, 

 and cautions about over-heating his balsam, when 

 there is not the slightest necessity for any of them, 

 I am of course aware that every mounter has his 

 pet method, and that constant practice will make 

 him perfect in its use ; but to the beginner, the 

 number of appliances and cautions are appalling, 

 and often deter him from making the attempt. For 

 many years I have used soft balsam oidy, and have 

 never known one of my preparations to change its 

 position on the slide, whilst any of them may be readily 

 rubbed with a chamois skin between thumb and 

 finger, without sustaining any injury, which Mr. 

 Kitton claims as an attribute of the hard balsam 

 slides. The following directions, if carefully fol- 

 lowed, will invariably result in success -. — Select 

 the finest Canada balsam and slowly evaporate it, 

 until upon cooling it assumes a brittle resiuous 

 consistency. Break the mass into small pieces, and 

 dissolve them in chemically pure benzole, until a 

 saturated solution about the consistency of rich 

 cream is formed. The specimen to ^be mounted 

 having been previously freed from moisture by 

 drying, or by being passed through weak and absolute 

 alcohol (the latter being by far the preferable 

 method), is finally to be placed in oil of cloves, and 

 carried from the latter to the slide, where, after 

 being properly arranged with needles, a drop of the 

 balsam is placed upon it, followed by a core in the 

 usual manner, and the whole laid aside to harden, 

 which will be accomplished in a few days. This 

 will be facilitated, if, after the lapse of twenty-four 

 hours, the slide be slightly warmed, the core pressed 

 carefully down with the forceps, and a small weight 

 laid upon it. The best finish for the edge of the 

 circle I have found to be made with a camel-hair 

 pencil dipped in the same balsam that is used in 

 mounting. It makes a very neat and handsome 

 finish, with of course no tendency to run in and 

 spoil the specimen, as is the case with all coloured 

 cements used for this purpose. The oil of cloves 

 is preferable to turpentine for mounting from, since 

 it is more readily miscible with the balsam, and 

 does not harden the specimens, which may be left 

 in it for a long while unchanged. I send you by 



