G3 



HAUDWICKE'S S CIE NCE-GOSSIP. 



many cells in the tiny pollen-grain, and a fluid called 

 I'ovilla, which gives the creative power to the ovule. 

 As soon as the pollen falls on the stigma it sends 

 forth a tube, long or short, as the case may be ; this 

 descends through the style, enters the ovary, reaches 

 the ovule, pouring in the fovilla, which gives life to 

 the future plant, which it preserves and nourishes 

 in the seed. The quantity of pollen in a plant is 

 astonishing; but when it is recollected the number- 

 less insects which feed on it, it can then be under- 

 stood that an all-wise Creator has made provision 

 for the different vicissitudes of the vegeiable king- 

 dom. In conclusion, my reason for selecting the 

 pollen of wild flowers instead of cultivated ones, 

 was, that there are many persons who have not ac- 

 cess to flower-gardens, especially those who live in 

 towns, and hence cannot investigate the subject for 

 themselves ; whereas, in the wide garden of nature, 

 all can easily go into the green fields and gather the 

 various flowers they care for, and by an examination 

 of their varied pollen-grain, can gain both informa- 

 tion and pleasure at a very small expense, granting, 

 of course, that they possess a microscope of moderate 

 magnifying power. The pollen-grains look charming 

 when illuminated with a parabolic reflector, which 

 throws them out in bold relief from the black back- 

 ground. Pollen-grains are very easily mounted by 

 shaking the grains off on a piece of black paper and 

 drying them carefully ; then mount them in a shallow 

 cell, on black paper, as an opaque object— the larger 

 kind are the best for this purpose, such as the Mal- 

 low, Hollyhock, &c. ; some of the darker-coloured 

 pollen can very well be mounted in balsam. This 

 operation requires to be carefully done, as the pollen, 

 being soft, can be seriously injured by over-pressure. 

 Having many of these specimens in my collection, I 

 can well testify that tliey are highly interesting, even 

 to those who have little interest in the subject, but 

 still admire them, on account of their eccentricity 

 of form. Ealph H. Westkopp, A.B., T.C.D. 



MICEOSCOPY. 



Aebobescent Slides.— If a few drops of the 

 solution of nitrate of silver be placed in a clean 

 copper cell cemented upon a glass slide, the growth 

 of crystals of metallic silver will immediately start 

 from the margin of the inclosed space and proceed 

 with great regularity towards the centre. Crystals 

 of the newly-formed compound, nitrate of copper, 

 will be deposited upon the surface of the silver as 

 the water evaporates, but by carefully immersing 

 the slide in clean water these will be redissolvcd, 

 and thus easily got rid of; when thus washed, the 

 arborescent silver may be mounted either dry or 

 in fluid, without in any way injuring or disturbing 

 it, as will almost invariably be the case when it is 

 precipitated upon a wire, as recommended by your 



correspondents in Science- Gossip, pp. 17 and 47. 

 Slides of arborescent lead may be prepared in the 

 same way from a solution of acetate of lead in a 

 zinc cell (or by " P. K.'s " plan with a small skred of 

 zinc). The similarity between the crystals of silver 

 and lead has frequently been remarked, and it will 

 be remembered that in nature these metals are con- 

 stantly found in combination. Arborescent silver 

 may also be prepared in great perfection by decom- 

 posing a solution of the nitrate by means of a weak 

 galvanic current. The terminal wires in this case 

 should be of platinum, and may be conveniently 

 brought upon the stage of the microscope 

 through two pieces of small glass tube mounted 

 in the same way as the stage forceps : they both 

 hold and insulate the wires and admit of movement 

 in any required direction. A commutator — or con- 

 trivance for breaking or reversing the current— in- 

 troduced between the jjlatinum terminals and the 

 battery will add very greatly to the interest of the 

 experiment ; a cell or trough containing the solution 

 should then be placed upon the stage and the ends 

 of the platinum W'ires immersed in it. On making 

 the connection with the battery an exquisitely 

 beautiful growtli of silver fern-like crystals viill 

 immediately take place upon the wire, connected 

 with the positive plate, a simultaneous growth of 

 prismatic crystals starting from the opposite wire. 

 On breaking the current the growth will instantly 

 cease, and on reversing it the curious cfi'ect of the 

 disappearance of the crystals in the inverse order 

 of their growth will be seen until all have been re- 

 dissolved, when a fresh growth will immediately 

 commence upon the"opposite wires ; and this alter- 

 nate growth and «;/-growth may be repeated any 

 number of times by a careful experimenter, to whom 

 details as to illumination, magnifying power, &c., 

 will be unnecessary here. It is, however, important 

 to mention that only a loealc current should be 

 employed, as otherwise the process goes on too 

 rapidly for convenient observation, and bubbles of 

 gas are apt to be disengaged from the wires, which, 

 in addition to disturbing the general tranquillity 

 of the fluid, will be sure to detach the crystals 

 themselves. A single cell of the smallest size 

 " Leclanche " battery, or one of "Walker's" con- 

 taining very diluted acid, will be found amply suffi- 

 cient for Ihe purpose. The foregoing experiment; 

 was detailed in the course of a paper read by the 

 writer at one of the early meetings of the Quekett 

 Club, but may yet be interesting to some readers 

 of Science-Gossip, seeing that the subject has 

 recently been revived in its pages. — R. T. L. 



Maltwood's PiNDER.— This little instrument, so 

 well known to microscopists, has perhaps not been 

 so generally adopted as it deserves to be. This- has 

 arisen from two causes, the first being the some- 

 what cumbrous method of registration usually 



