664 



SCIENTIFIC RECREATIONS. 



Fig. 743. Stomata. 



The tissue of the cuticle, or epidermis, which externally covers all parts 

 of the plant while they remain green, is of a peculiar nature, and demands 



special consideration. It is formed of flat tubular 

 cells, very much compressed, and in close contact, 

 with the exception of some parts where the stomata, 

 or mouths, are placed. In fig. 742 a section of 

 the leaf is represented, the large transparent empty 

 cells of the epidermis, and above these the paren- 

 chymatous cells of the leaf filled with greenish- 

 coloured granules. In four places (fig. 743) stomata 

 (ssss) are seen, which have their openings sur- 

 rounded by parenchymatous cells disposed in semilunar forms. Under each 

 stoma (mouth) there is a hollow space which is connected with the intercel- 

 lular passages of the leaf. These stomata, represented in fig. 743, are so 

 numerous on the under side of the leaf, that hundreds have been counted in 

 the space of a square line. Through these minute organs an intimate con- 

 nection exists between the interior of the plant and the external air. 



The epidermal cells not unfrequently exhibit very abnormal formations. 

 When much extended in length they appear as hairs which are frequently 

 branched, and in many plants they contain an irritating sap (in the nettle, 

 for example). Bristles, prickles, glands, warts, and especially the substance 

 which forms the well-known cork, are all due- to the metamorphosis of this 

 exterior integument. 



FLOWERING PLANTS. 



Flowering plants have certain distinct features which cannot be mistaken, 

 for they grow well above ground, and can easily be examined. There are a 

 hundred-thousand different species of flowering plants, and a visitor to Kew 

 can study them there. Any child can tell a flower when he sees it, but a 

 flowering plant is no more restricted in BOTANY to actual bright blossom- 

 ing plants, than 'the term rock in GEOLOGY means a mass of stone only. 



Fig. 744. Water lily. 



Fig. 745- Transformation of petals into stamens in 

 white water lily. 



Flowering plants may be either very gorgeous or very simple; and so 

 long as they contain a reproductive apparatus they are flowering plants. The 

 rose is a flowering plant, but the oak is equally one. The beech tree and 

 the primrose are classed under the same heading. 



