THE STUDY OF TYPICAL FRUITS. 183 



(4) The central column or axis of white pithy tissue. 



(5) The location and attachment of any seeds that may be encountered 

 in the section. 



Make a sketch to illustrate these points, comparing it with Fig. 181. 



Study the section with the magnifying glass and note the little spherical 

 reservoirs near the outer part of the skin, which contain the oil of lemon 

 which gives to lemon-peel its characteristic smell and taste. Cut with 

 the razor a thin slice from the surface of the lemon-peel, some distance 

 below the section, and at once examine the freshly cut surface with a 

 magnifying glass to see the reservoirs, still containing oil, which, how- 

 ever, soon evaporates. On the cut surface of the pulp (in the original 

 cross-section) note the tubes in which the juice is contained. These 

 tubes are not cells, but their walls are built of cells. Cut a fresh section 

 across the lemon, about midway of its length and sketch it, bringing out 

 the same points which were shown in the previous one. The fact that 

 the number of ovary cells in the fruit corresponds with the number of 

 minute knobs in the depression at its base is due to the fact that these 

 knobs mark the points at which fibro-vascular bundles passed from the 

 peduncle into the cells of the fruit, carrying the sap by which the growth 

 of the latter was maintained. 



Note the toughness and thickness of the seed-coats. Taste the kernel 

 of the seed. 



Cut a very thin slice from the surface of the skin, mount in water, 

 and examine with a medium power of the microscope. Sketch the 

 cellular structure shown and compare it with the sketch of the corky 

 layer of the bark of the potato tuber. 



Of what use to the fruit is a corky layer in the skin ? (See § 230 for 

 further questions.) 



216. A Legume, the Bean-Pod.^ — Lay the pod flat on the table and 

 make a sketch of it, about natural size. Label stigma, style, ovary, calyx, 

 •peduncle. 



JIake a longitudinal section of the pod, at right angles to the plane in 

 which it lay as first sketched, and make a sketch of the section, showing 

 the partially developed seeds, the cavities in which they lie, and the solid 

 portion of the pod between each bean and the next. 



Split another pod, so as to leave all the beans lying undisturbed on 

 one-half of it and sketch that half, showing the beans lying in their 



1 Any species of bean (Phaseolus) will answer for tMs study. Specimens in tlie 

 condition laiO"wn at tlie marliets as " siiell-beans " would be best, but these are not 

 obtainable in spring. Ordinary " string-beans " will do. 



