196 BOTANY FOR BEGINNERS CHAP. 



with the torn surface below, and examine under a low power. 

 Note 



(i) The conical-shaped outline of the cells. 



(ii) The cells contain coloured cell-sap. There are no chromoplasts 

 present. 



EXPT. 176. Cut transverse sections through a sepal of the Wall- 

 flower, mount the thinrtest in water, and examine with the high power. 

 Note 



(i) The epidermis on both the upper and lower surfaces. 



(ii) The mesophyll between the upper and lower epidermis, it 

 contains vascular bundles. 



EXPT. 177. Harden a few petals of the Wallflower in alcohol, and 

 cut transverse sections. Select the thinnest and mount in glycerine. 

 Examine under the low power. Note 



(i) The short hairs growing out from the epidermal cells. These give 

 the characteristic appearance to the petals because they reflect the 

 light. 



(ii) The vascular bundles are slender, but consist of xyleni and 

 phloem. 



(iii) The mesophyll is built up of parenchyma cells. 



(iv) The epidermis contains no stomata. 



EXPT. 178. Examine with the hand-lens the base of a single petal 

 of the Buttercup. Note 



(i) The pocket-like nectary which secretes honey. 



Place it in alcohol for a short time, and mount in water. Examine 

 it with a low power and reflected light. Note 



(ii) The vascular bundles, which give to the petal a veined appearance. 



(iii) The epidermis, which consists of small but regularly arranged 

 cells. 



(iv) The colouring matter has nearly all disappeared. 



The Essential Floral Organs. The androecium and 

 gyncecium form the essential floral organs. They are called the 

 essential organs of the flower, because without them no seeds 

 can be produced. The calyx and corolla are not essential for 

 the formation of seeds, since many plants which have only 

 stamens and pistil produce seeds. The calyx and corolla do, 

 however, perform useful work in protecting the essential organs 

 from loss of heat as well as from dew and rain ; they also by 

 their colour, perfume, and shape attract insects to the flower. 



The Structure of the Androacium. The andrcecium 01 

 a flower consists of modified leaves, which bear very little re- 

 semblance to foliage leaves. Each stamen is, as a rule, filiform 

 in shape, and consists of a filament or stalk bearing an anther at 

 the apex. They have no vegetative function to perform, but are 



