CHAPTER VII. 



MICROSCOPIC STRUCTURE OF HIGHER CRYPTOGAMIA. 



256. From those simple Protophytes, whose minuteness causes 

 their entire fabrics to be fitting objects for Microscopic examina- 

 tion, we pass to those higher forms of Vegetable life whose larger 

 dimensions require that they should be analyzed (so to speak) by 

 the examination of their separate parts. And in the present Chap- 

 ter we shall bring under notice some of the principal points of 

 interest to the Microscopist which are presented by the Crypto- 

 genic series ; commencing with those simpler Algte which scarcely 

 rank higher than some of the Protophytes already described, and 

 ending with the Ferns and their allies, which closely abut upon 

 the Phanerogamia or Flowering Plants. In ascending this series, 

 we shall have to notice a gradual differentiation of organs ; those 

 set apart for Reproduction being in the first place separated from 

 those appropriated to Nutrition (as we have already seen them to 

 be in the Chavacece) ; while the 

 principal parts of the Nutritive ap- 

 paratus, which are at first so blended 

 into a uniform expansion or Thallus 

 that no real distinction exists between 

 Root, Stem, and Leaf, are progres- 

 sively evolved on types more and 

 more peculiar to each respectively, 

 and have their functions more and 

 more limited to themselves alone. 

 Hence we find a differentiation, not 

 merely in the external form, but 

 also in the intimate structure of 

 organs ; its degree bearing a close 

 correspondence to the degree in 

 which their functions are respec- 

 tively specialized or limited to par- 

 ticular actions. Thus in the simple 

 Ulvce (Fig. 147), whatever maybe Mesogloza verrmcularis. 



the extent of the Thallus, every part has exactly the same 



Fig. 160. 



M 



