146 



HARDWICKE'S SCIENCE- GO SSIP. 



thin knife, lay the blade against your finger-nail, 

 and cut gently and cautiously down to the paste- 

 board, lest the sections should be jerked away. 

 The thinner the slices are cut, the better. They 

 cannot be too thin. It, is better to cut eight or ten 

 slices, because they afford more scope for observa- 

 tion, and it is as easy to cut a dozen as to cut one, 

 by moving the finger-nail gently backward between 

 each cutting. 



If great care be not taken in cutting the sections, 

 the central part, often of very lax texture, may be 

 torn, or even displaced, so that the frond appears to 

 be hollow. This appearance is always to be dis- 

 trusted. And now will be found the advantage of 

 having cut many sections. Close observation of all 

 these will seldom fail to discover, not only traces of 

 the central stratum, but probably a good section of it, 

 from which the structure of the frond may be 

 ascertained. If all the sections fail in showing the 

 central stratum in perfect condition, other sections 

 must be cut until this object is attained. A little 

 practice will render this operation easy. 



"When you have cut as many sections as you wish, 

 tilt the cardboard gently on to one of the pieces of 

 glass, using the knife or needle to remove the 

 sections if necessary. Add a small drop of water. 

 If you put too much water, the pieces of alga 

 will float about. Superfluous water may be removed 

 with a piece of rag or dry hair pencil. Perhaps it 

 may be found more convenient to put the water on 

 the glass, and then remove the sections on to the 

 wet part of the glass ; they arc then less likely 

 to scatter and be lost. Place the glass on the fieid 

 of the microscope, not using too high a power, 

 as you require a large field. The needles may now 

 be useful to place the sections conveniently near 

 together, or to turn them into a horizontal position, 

 as they are very apt to lie on their edges. It 

 is very beautiful to see the sections expand, which 

 they do in some alga} more quickly thau in others. 

 Some require a few minutes only for this purpose, 

 others an hour or two. In the latter case, put 

 a watch-glass or inverted wine-glass over the 

 sections (having previously removed the glass on 

 which they are from the microscope), to prevent 

 evaporation. If the sections do not open properly, 

 add a drop of the muriatic acid, which will generally 

 cause the sections to open, though it will deprive 

 them of colour. The best way to apply the acid, is 

 to dip the end of the stick of the match into the 

 bottle, so as to take up a very small quantity only. 

 Then cork the bottle carefully. If you use the 

 microscope in a sloping position, the sections with 

 the water and acid should be placed on a glass 

 with a hollow sunk in it, to avoid injuring the brass 

 work of the microscope. It is generally an advan- 

 tage to place another glass on that which holds the 

 sections. 

 Longitudinal sections of small plauts are more 



I 



difficult to make thau transverse sections. The 

 best plan, as the late Mrs. Gatty used to say, is to 

 choose a forked branch, that you may have some- 

 thing to hold. Sometimes an oblique section will 

 be easier to hold and cut than a longitudinal one. 



Of fruit, when large enough, sections may 

 be cut both horizontally and vertically. When 

 making a vertical section of the fruit,, the best plan 

 is, to cut through the frond as well as the fruit. It 

 will then be seen exactly how one part is attached 

 to the other. In many cases'it is preferable, instead 

 of cutting sections, or in addition to so doing, to 

 press the fruit gently between two pieces of glass, 

 and you will then see the structure of the receptacle, 

 and the shape of the spores and tetraspores which 

 exude under the pressure. 



Having completed your examination of the 

 sections and fruit, you should now make careful 

 drawings of both. These drawings should be put 

 away with the specimens. They will be useful not 

 only in identifying the plant, but also for future 

 reference. 



It may be as well to mention, before I conclude, 

 that I have tried an instrument used by micro- 

 scopists for cutting sections, and found it not nearly 

 so well adapted for algai as the more simple plan I 

 have just described. Patience and practice will 

 enable you to cut clean and thin sections; but 

 when you have accomplished this object, a greater 

 difficulty still remains to be overcome, namely, 

 to understand the structure which the microscope 

 has revealed, and to refer the plant under examina- 

 tion to its proper order, genus, and species. 



THE DOUBTFUL PLANTS OF GREAT 

 BRITAIN. 



TT has often been a matter of surprise to me, and 

 J- no doubt to many besides myself, that no one 

 has attempted to throw any light on the history of 

 those plants which are considered doubtful natives 

 of the British Isles. When a plant is said to have 

 been introduced, is it impossible to discover when, 

 where, and by whom it was first brought into 

 Britain, so as to give some solid reason for its not 

 being admitted into the list of our indigenous 

 plants ? How is it that no one has endeavoured 

 to throw some light on this disputed point? The 

 longer such an investigation is postponed the 

 more difficult it will be to arrive at anything like 

 a satisfactory solution. 



When we recollect that a century ago the facili- 

 ties of travelling were comparatively few, that 

 many parts of the kingdom were almost isolated, 

 and therefore but rarely visited, it seems highly 

 probable that plants might be flourishing in various 

 secluded spots in our islands that no botanist ever 

 found. In more recent days the deep cuttings of 



