52 THE STORY OF THE PLANTS. 



merely a leaf, but also at the s;ime time a flower, 

 a seed, a root, a branch,- and everything. In 

 other words, in very simple plantslT single cell 

 does rather badly, everything which in more 

 advancecTand developed "plan is is better done by 

 distinct and highly-adapted organs. The whole 

 evolution of plants consists, in fact, injbhe tellmg 

 off of particular parts to do betterwhat $ie 

 primitive cell did for itself but badly. Above 

 the very simple plants which consist of a single 

 cell come other plants, which consist of many 

 cells glace^^n^^n^ri^togejher^ as in the case 

 of the HhaTr like" water- weeds ; and above these 

 again come other and rather higher plants, in 

 which the cellular tissue assumes the form of a 

 flat and leaf-like blade, as in many broad sea- 

 weeds. None of these, however, are called 

 leaves in the strict sense, because they consist 

 of cells alone, without any ribs or supporting 

 framework. The higher types, however, like 

 ferns and flowering plants, have such ribs or 

 frameworks, made of that stiffer and tougher 

 material called vascular tissue. This is the 

 most general distinction that exists between 

 plants ; the higher ones are know r n as Vascular 

 Plants, including all those with true leaves, such 

 as the common trees, herbs, and shrubs, and the 

 ferns and grasses in fact, almost all the things 

 ever thought of as plants by most ordinary 

 observers ; the lower ones are known as Cellular 

 Plants, and include the kinds without true 

 . leaves or vascular tissue, such as the seaweeds, 

 fungi, and microscopic plants only recognised 

 as a rule by botanical students. 



