2 CLASSIFICATION. 



In modern systems, therefore, we find a more honourable 

 position assigned to the Algae ; and in the ' VEGETABLE 

 KINGDOM' of Professor Lindley they (together with the Clia- 

 racea, which I regard as vegetables of higher type), consti- 

 tute his first Alliance, consisting of five natural orders, 

 Diatomacea:, Confervacece, Fucacea, Ceramiacece and Cha- 

 raceat. To the four first of these groups I confine my idea 

 of the class Algse : the last, though with a simplicity of frond 

 equal to that of some of the less perfect of the Algae, has or- 

 gans of fructification so much more developed than any met 

 with among the highest Algae, that I cannot consent to in- 

 clude it in the class. If we adhere to the established maxim 

 that the fructification of plants and not their organs of nutri- 

 tion ought to be our guide in classification, we shall probably 

 place the Characeae more nearly on a level with the Hepa- 

 ticae than with any section of Algae. Their exact position 

 in the scale of organization is still, perhaps, doubtful. To 

 me they seem like the remains of a ruined alliance whose 

 species are diminishing, and of which other members, which 

 would connect it with neighbouring alliances, are lost. Such 

 cases are not without parallel in the vegetable world. Equi- 

 setacece is an instance of a small group nearly equally isolated ; 

 and we have good reason to suppose that both it and Chara- 

 cece were much more abundant and of a higher type, in more 

 remote periods than at present. Podostemacea, among Exo- 

 gens, may also be mentioned as an example of the combina- 

 tion of considerable perfection of the floral organs, with the 

 greatest imperfection of foliage and this order seems fully 

 as much below the average development of Exogens as the 

 Characeae is below that of the Hepaticae. 



Admitting the improvement of breaking up the old order 

 Algae into several, it may yet be questioned whether the 

 groups of genera brought together under the above names 

 are natural orders, or assemblages of a higher value. The 

 first consists of two very distinct groups of plants, the 

 Diatomacece, whose epidermis is formed of silex; and the 

 Desmidiacea, in which the external skin consists of simple 

 cellulose. These two groups may either be regarded as 

 well-marked sub-orders, or as separate orders of a common 

 alliance, namely, of the Chlorospermeae or green Algae (Con- 

 fervacea, Lindl.). 



The contents of the three following groups are very much 

 more heterogeneous. Confervaceae (synonymous with our 

 Chlorospermeae) contains all the green Algae ; Fucacea (our 



