Xll 



PREFACE. 



vegetation you see around you ; and remark how 

 different it is from our own. Here is a plain 

 covered with a plant which resembles number- 

 less yards of green figured ribbon, in a state of 

 entanglement. If you examine the substance, 

 you find it composed of cells linked together 

 in myriads, each cell containing granules which 

 form the seed ; these cells in time break up, 

 the imprisoned grains come forth, and from them 

 arise new plants in countless numbers. Here is 

 another, much thicker, and of a different pattern. 

 Now we come to one, which, instead of being 

 round, like the others, is three-sided. Then look 

 on this- have we anything to compare to it ? You 



