72 STRUCTURE AND PHYSIOLOGY OF SEED PLANTS 



C. Eemove the bit of stem and dried-up calyx from the base 

 of the fruit ; observe, above the calyx, the disk on which 

 the pistil stood. Note with the lens and count the minute 

 whitish, raised knobs at the bottom of the saucer-shaped 

 depression left by the removal of the disk. What are they ? 



D. Make a transverse section of the lemon, not more thau a 

 fifth of the way down from the stigma end, and note : 



1. The thick skin, pale yellow near the outside, white within. 



2. The more or less wedge-shaped divisions containing the 

 juicy pulp of the fruit. These are the matured locules of 

 the ovary ; count these. 



3. The thin partition between the cells. 



4. The central column or axis of white pithy tissue.- 



6. The location and attachment of any seeds that may be 



in the section. 

 Make a sketch to illustrate these points. 



E. Study the section with the lens and note the little spherical 

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

 oU of lemon whict gives to lemon peel its characteristic smell 

 and taste. With the razor cut a thin slice from the surface 

 of a lemon peel, some distance below the section, and at once 

 examine the freshly cut surface with a lens to see the reser- 

 voirs, still containing oil, — which, however, soon evapo- 

 rates. On the cut surface of the pulp (in the original cross 

 section) note the tubes or sacs in which the juice is contained. 

 These tubes are not cells, but their walls are built of cells. 



F. 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 locules 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 flower stalk into the cells of the fruit, 

 carrying the sap by which the growth of the latter was 

 maintained. 



