153 



APPENDIX ON PRACTICAL WORK. 



united at base. Carpels, generally 3. Placentation, axile. Fruit, 

 a capsule. 



Exs. — Harebell, Canterbury bell. 



II.— Anatomy. —Root (p. 14). Stem (p. 29).— Try to follow, mainly 

 by longitudinal slicing, the course of the bundles in a piece of aspara- 

 gus stem (cf. fig. 5, C). Leaf. — The distribution of vascular bundles is 

 plainly seen in most herbaceous forms, and may be rendered still more 

 plain "by bleaching in spirit, and then soaking in chloral hydrate. 

 Compare the distribution in monocotyledons and dicotyledons. 



III. Histology. — A compound microscope is necessary for this. 

 Browning's field -microscope, shown in fig. 61, will answer the purpose 



for a beginner, and even if 

 a larger microscope is after- 

 wards purchased, will always 

 be useful for carrying about. 

 It consists of a stand, eyepiece, 

 and objectives. The stand is 

 supported by three legs, and 

 carries a sliding tube above, 

 and a perforated plate or 

 stage below, upon which the 

 object to be examined is 

 placed. Below the stage 

 swings a small concave mir- 

 ror, from which light can be 

 reflected upwards through 

 the aperture. The eyepiece 

 slips into the upper end of 

 the tube, while the objective 

 screws into the lower end. Objectives are named, according to the 

 distance at which they must be placed from the object, two-inch, 

 inch, half-inch, quarter-inch, &c, &c. Inch and half-inch objectives 

 will be sufficient for elementary purposes, and will be called low power 

 and high power in the rest of this Appendix. The price of Browning's 

 field-microscope, with one eyepiece and the two objectives named, also 

 with case and forceps (as in figure), is £2, is. 6d. Suitable glass slijis 

 (say two dozen) and cover-glasses (^ oz. of small squares) can be obtained 

 for a small sum of the same maker. 1 



We may examine objects in two ways : (1) by reflected light ; (2) by 

 transmitted light. It is perhaps easier to commence with the former. 



(1.) Opaque objects are best suited for viewing with reflected light. 

 Pollen grains (preferably of mallow or hollyhock), small seeds, or liat 

 bits of leaf with hair structures are good examples. Place one of these 

 objects on a piece of black paper on the centre of a glass slip. Screw 

 on the low power, and pull out the inner half of the microscope tube 

 till a groove upon it is seen. Put the slip under the two spring-clips of 

 the stage, and turn the mirror so that it reflects no light through the 

 hole. To focus, slide down the tube near to the object, apply the eye to 

 the eyepiece, and slide up the tube till the object is seen. This sliding 

 action is the coarse adjustment. The fine adjustment is brought into 



1 63 Strand, London, S.W. 



