38 VEGETABLE ORGANS. 



tain pistils only, although most flowers contain both 

 organs. When the stamens and pistils occur in sepa- 

 rate flowers on the same plant, the plant is said to be 

 monoecious (fwvos, single, ottfo?, family) ; when all the 

 flowers of distinct plants contain either stamens only 

 or pistils only, the plant is dioecious (St?, twice, ol/cos) ; 

 and when the stamens and pistils occur together in all 

 the flowers of the same plant, the plant is said to be 

 hermaphrodite. These terms had their origin in the 

 idea that the differences of plants in respect to these 

 organs were analogous to those of the sexes in animals. 

 All the parts of a flower have their special uses : thus 

 the calyx and corolla protect the delicate organs en- 

 closed by them, until they attain maturity. The 

 petals also, by their brilliant colours, attract insects 

 which feed upon or collect the honey of the flowers ; 

 these at the same time conveying the pollen which 

 adheres to their bodies from one flower to the stigma 

 of another. The stamens and pistils are organs of 

 fructification, it being essential for the fertilization of 

 the flowers that the pollen should come into contact 

 with the stigma. We will now consider some inter- 

 esting points of structure in these organs. 



Petals. The petals often form most beautiful mi- 

 croscopic objects, on account of the curious shape 

 and structure of the cells of their epidermis, and the 

 splendid tints of the colouring matters contained in 

 them. As petals are mostly too thick to allow of the 

 cells being distinctly seen in the entire state, a little 

 cut should be made in them while gently stretched 

 on the finger, and the epidermis carefully stripped off 

 with forceps; the strip should then be laid on the 

 slide in water as usual : in this way the curious 

 patterns of the epidermic cells will become very dis- 

 tinct. The petals of a red geranium (Pelargonium) 

 may be used to illustrate them (PL I. fig. 24) . The 

 structure may be best understood by reference to the 

 epidermis of the leaf of a geranium (PL I. fig. 13), 



