structure. 41 



CHAPTER V. 



FERN STRUCTURE. 



Be it ours to meditate, 



^ i^ % if. 



And to the beautiful order of thy works 

 Lnarn to conform the order of our lives. 



— Bryant. 



76. Tissues. — The life history of every plant commences in a 

 single cell, and all the complications of vegetable growth depend 

 on two simple processes, viz : the enlargement of individual cells 

 to their full size, and their multiplication by division. The lowest 

 forms of vegetable life consist of a single cell, either globular or 

 elongated. Those of a somewhat higher grade consist of a single 

 row of cells, or at most a single layer ; while still higher forms of 

 growth consist of masses of cells variously grouped together and 

 specialized by differentiation from the typical form and character. 

 These specialized cells give rise to the various forms of vegetable 

 tissue. The earliest tendency to differentiation is seen in the ar- 

 rangement of the outer row of cells to form a boundary wall. In 

 higher forms of growth the interior cells tend to form one or more 

 series of string-like rows surrounded by the normal cellular tissue. 

 We thus reach the basis of the classification of vegetable tissues 

 into three groups : (a). Epidermal tissue. \b). Fundamental 

 tissue, [c.) Fascicular or Vascular tissue. (Fig. 28). The first 

 and second are common to both ferns and mosses. The last is 

 first seen in the ferns, where it is a character so constant that it 

 serves as the basis for separating the so-called "vascular " Cryp- 

 TOGAMiA from other flowerless plants. These three forms of tissue 

 may be seen by examining a thin cross section of the stipe of a 

 living fern with the microscope. 



77. Roots.— Roots are constantly produced as the rhizoma 

 advances, and consist for the most part of little fibrils which are 

 naked for a short distance from the apex in order that they may 

 freely absorb the moisture from the earth. The epidermis is also 

 thin and usually consists of a single layer of small cells. It differs 

 from that of the rest of the plant in having no stomata (81). As 

 the apex continues to grow, the epidermis of the part behind be- 

 comes harder and frequently develops hairs or more frequently 

 irregular scales. 



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