60 



ORGANOGRAPHY. 



Fig. 146. 



Fig. 147. 



Fig. 146. Gland from the leaf of the common Rue (Ruta graveolens). 

 g. Gland surroiiiiding a cavity, I, and itself surrounded by the epider- 

 mis, e, and the ordinary cells of the leaf, we. Fig.X^I. rr. Internal 



glands from the rind of an orange. 



In some cases they are of small size, as in the leaves of the 

 Eue, {fig. 146), Myrtle, Orange, Lemon, and St. John's Wort. 

 They may be readily observed by holding such leaves up against 

 the light, when they appear as little transparent spots. This 

 dotted transparent appearance is due to the oily matters they 

 contain refracting the light in a diiferent manner to the parts 

 surrounding them. In some instances these glands are of large 

 size, and project more or less beyond the surface of the epidermis 

 in the form of little tubercles, as on the rind of the Orange {fig. 

 147), Lemon, and Citron, Internal glands are very common in 

 many plants, besides those above mentioned : thus in all the 

 Labiate Plants, as Mint, Marjoram, Thyme, Rosemary, Sage, &c, : 

 and it is to the presence of the secretions they contain that such 

 plants owe their value as articles of domestic economy or as 

 medicinal agents. 



Fig. 148. 



Fig. 149. 



Fig. 150. 



Mg. 148. Petal of the Ranunculus with a nectary at 

 its base. — Fig. 149. Petal of Crown Imperial (^Fri- 

 tillaria imperialift), with a nectariferous gland at 

 Its base. — Fig.XbO. Branch of a species of Wil- 

 low. 1,1. Leuticels. c,c. Buds. 



