36 MINUTE MARVELS OF NATURE 



Cells, then, are the bricks which build up the 

 plant edifice. The simplest plant is built of one 

 brick, as we have seen ; and next in simplicity 

 come plants composed of a few simple cells united 

 together in a chain as previously considered. 

 Complexity begins when a plant exhibits cells of 

 different kinds, each kind fulfilling specific functions 

 in the life of the plant. The apple-pulp cells are 

 very simple in structure, but much more compli- 

 cated tissues are found in other parts of the parent 

 tree. To show the differentiation of cells for 

 various purposes in plant economy, we may take 

 almost at random any insignificant fragments of 

 any plant. 



Every one has observed, for instance, that 

 plants are frequently hairy on leaves, flowers or 

 stems, &c., and Fig. 23 shows a few hairs from 

 the throat, as we call it, of the common yellow 

 pansy. These hairs are in reality single cells, 

 which, instead of remaining as flat skin-cells of 

 the petal, have poked themselves out into elon- 

 gated shapes with irregular knotted swellings. 

 To the naked eye they look like minute hairs, 

 but under the microscope more closely resemble 

 rugged glass tubes, being quite transparent and 

 filled with granular matter like the cells in their 

 more simple forms. Hundreds of these uni- 

 cellular hairs, with others of entirely different 



