>32 



KNOWLEDGE • 



[March 20, 1885. 



there are two cutting surfaces, one flat, and the other more 

 or less rounded. 



(?) Round, in which if a cross section be taken at any 

 part of its length we shall get a circle. Round files, when 

 small, are called rattail. 



(/') Crossing (shown in section in Fig. G, page 103), in 

 which there are two rounded cutting surfaces, struck from 

 diflerent radii. "~' " 



The young electrician can purchase his files, as he may 

 r^'quire them, at any tool shop. They are inexpensive 

 tools. 



PLEASANT HOURS WITH THE 



MICHUSCOPE. 



M 



By Hexet J. Slack, F.G.S., F.R.M.S. 



J E3SRS. CARTER i CO., the well-known gardeners 

 and flori-its, have issued boxes of seeds interesting 

 to microscopists. The largest of the three collections con- 

 tains 100 specimens, some very curious, and many of con- 

 siderable beauty as lo^-power objects. A few seeds are 

 [iretty generally known to possessors of microscopes, but 

 this is, I believe, the tirtt time an opportunity has been 

 offered of making a comprehensive study of many genera 

 andjSpecies. The seeds are sent out in little wooden boxes, 

 each having a number on its lid by which reference can be 

 made to a list of names on the inside of the cover of the 

 square box that holds the lot. There is no method in the 

 arrangement, and the first thing the buyer had better do Ls 

 to pencil the bof.om of each box with the number found on 

 the lid. This enables the covers of several to be taken off 

 at one time without risk of their being subsequently mis- 

 placed. After this, these who are not well up in botanical 

 names and classification should refer to such a book as 

 " The Treasury of Botany," and mark the list with a few 

 letters intimating the family each seed belongs to. Abbre- 

 viations are handy, such as comp. for composite ; ranun. for 

 ranunculus or daisy family, and so forth. 



Amongst the Composites will be found many of the 

 prettiest and most curious objects to be viewed as wholes 

 with powers, according to their size, from four inches up to 

 one inch, or two-thirds. When, as is often the case, the 

 pappus hairs are elegantly branched, or adorned with little 

 imbricated and pointed scales, they are worth viewing with 

 higher oVjjeotives, and may be mounted in Canada balsam. 



There is a great deal of chai-acter in the downy sails 

 which enable the winds to carry off the seeds of the thistles 

 and similarly-provided Composites ; and botanists refer to 

 them as offering specific distinctions. Some seeds of Com- 

 posites, however, are destitute of these appendages, and we 

 find in Carter's collection a very pretty one — that of the 

 handsome garden flower, Calliopsis tinctoria. The seeds of 

 this plant arc flattish, boat-shaped, in-curved objects, about 

 — '.Tth of an inch long, beautifully marked with minute pits, 

 and sprinkled over with whitish dots like little bits of 

 sugar. This is a fine object with a magnification of about 

 fifty linear, and a strong light to show up its bright brown 

 and blackish hue. 



One of the finest of the Composite see.ls is that of Cijaniis 

 major, the Cornflower. This requires very little magnifica- 

 tion, but a bright light. It is like a beautifully-made 

 shuttlecock, the solid conical part about a quarter of an 

 inch long, surmounted with a fine group of hairs. The 

 colours are rich brown. The figure herewith shows its 

 appearance as a whole, slightly magnified, and also that of 

 a portion of one of the hairs magnified fifty times linear. 

 When mounted in balsam, these hairs are richly-coloured 

 polariscope objects. 



The seeds of Cyanus mirwr, also in the collection, are 

 extremely pretty, but smaller, and of light hue. Another 

 Composite seed,'which is a favourite with microscopists who 

 know, is that of Sphenogyne speciosa. It is a Cape plant, 

 said to be handsome in gardens, and some reader may 

 know it I do cot, and therefore quote " The_ Treasury of 

 Botany," which says of the members of this genus :— - 

 "They have an imbricated involucre, the inner scales of 

 which, or all, have a dilated scarious termination ; the 

 receptacle is paleaceous (scaly), and the pappus simple in a 

 single row of obovate, or wedg»:-haped, blunt scales, which 

 become opaque white when mature. They have large, 

 spreading flower-heads of an orange colour, barred with 

 black." 



M^< >-,N iJ,f^r 





Cyanus major seed. x 50. 



The seed, arranged for the microscope, looks like a 

 complete plant. The scales at the top should be neatly 

 spread out, and thus form a cabbage-shaped flower; the 

 solid part looks like a stem, and a tuft of hairs at the 

 bottom has the aspect of fibrous roots. 



A great many of the hairy appendages of Composite 

 seeds reflect light very strongly, and some of the thistles 

 fight their battle of life so vigorously as to take possession 

 of considerable spaces to form large colonies. The winds 

 often carry off swarms of the downy objects, and an inci- 

 dent of this kind was the probable cause of a curious tele- 

 scopic observation accidentally made by the writer some years 

 ago. The telescope was pointed to look at one of the planets 

 in the daytime, when the sky was clear and the sun brilliant, 

 and for several hours appearances like showers of falling 

 stars were visible. They were momentary flashes of white 

 light, most sharply seen when the instrument was focussed 

 to show the planet, thus indicating that they were sufli- 

 ciently far off to be seen with horizontal rays only. After 



