1J2 INTRODUCTION TO CEYPTOGAMIO BOTANY. 



convey any profounder notion. In fact the differently coloured 

 species which are referred to one genus on account of perfect 

 simUarity of structure, may not, as observed before, in reality'all 

 belong to the same category ; but as we are restricted in natural 

 history to certain definitions, and bodies which agree with one 

 another, as far as those definitions, go, must needs be asso- 

 ciated, we must be content to leave the matter as it is, till 

 a profounder knowledge of the objects of creation may enable 

 us to unravel the order which has been observed in their crea- 

 tion, and the natural relations by which small and great form 

 one harmonious whole. 



92. Chlorosperms are divisible into several distinct and 

 well-marked groups, which are again divisible in accordance 

 with nature. The object of the present treatise, however, is not 

 so much the description of each individual form, as such an indi- 

 cation of the more prominent features as may either give some 

 general knowledge of the structure of Cryptogams, or render 

 comparison with higher types simple, and at the same time 

 certain. I shall therefore confine myself to the larger divisions, 

 referring those who wish for more specific information to par- 

 ticular treatises, for which som.e facility will, I trust, be given 

 by the subjoined lists of the more prominent works and 

 memoirs in each subject. 



93. Now there are at least twelve salient groups which 

 cannot fail to attract the attention of every student, of which 

 that which contains the simplest forms shall come first. The 

 others cannot follow exactly in the order of their affinities, as no 

 linear arrangement can possibly be consonant with nature. 

 The groups wUl be the following. 



1. PahnellecB. 2. Desmidiacece. 3. Diatomacem. 4. Con- 

 fervaeece. 5. Batrachospermece. 6. Hydrodictyce. 7. Nos- 

 tochince. 8. Oscillatorice. 9. Conjugatce. 10. Bulbochcetew. 

 11. Siphonew. 12. Ulvacece. These again form three dis- 

 tinct groups, the first consisting of those species in which 

 the individual cells, rarely forming compoimd threads or 

 expansions, are the prominent features ; the second of those 

 which are essentially filamentous ; and the third of species 

 essentially foliaceous. 



