28 THE STORY OF THE PLANTS. 



they are specks of green jelly, enclosed by a 

 cell-wall, alone and isolated. In such cases, 

 when the cell grows big and divides in two, each 

 half floats off as a separate cell, or a separate 

 plant, and continues to divide again and again, 

 as long as it can get a sufficient amount of 

 carbonic acid and sunlight. But in some 

 instances it happens that the new cells, when 

 budded out from the old ones, do not float off 

 in water, but remain hanging together in long 

 strings or threads, in single file, as you may see 

 in certain simple forms of hair-like pond- weeds. 

 These weeds consist of rows of cells, stuck one 

 after another, not unlike rows of pearls in a 

 necklace. Of course the individual cells are too 

 small to see with one's unaided eye ; but under 

 a microscope you can see them, joined end to 

 end, so as to form a sort of thread or long line 

 of plant- cells. This is the beginning of the 

 formation of the higher plants, which consist, 

 indeed, of collections of cells, arranged either 

 in rows or in flattened blades, or many deep 

 together in complicated order. 



However, the higher plants differ from the 

 lower ones in something more than the number 

 and complexity of the cells which compose them. 

 They are very varied ; and their variety adapts 

 them to their special circumstances. For 

 example, desert plants, like the cactuses, have 

 thick and fleshy leaves (or, rather, jointed stems) 

 to store up w^ater, with a very tough skin to 

 prevent evaporation. The flowers of each 

 country, again, are exactly adapted to the 

 insects of that country; and so are the fruits 



