12 FIRST GROUP. 



CLASSIFICATION OP THE THALLOPHYTES. The systematic division 

 of the Thallophytes was once founded entirely on characters derived from the habit 

 of the plants, and three classes were distinguished, Algae, Fungi, Lichens. It is now 

 established that the Lichens do not form a special class distinct from Algae and Fungi, 

 but must be ranked with Fungi, the much larger number of them with the Ascomycetes, 

 two genera only belonging to the Basidiomycetes. There are therefore only two 

 classes to be distinguished, Algae and Fungi. If we desire to retain these two 

 classes in their traditional form, we can separate them from one another only by 

 regarding all Thallophytes which contain chlorophyll as Algae, all those that have 

 no chlorophyll as Fungi. But this does not supply a satisfactory principle of 

 classification. 



The first point to note is that the presence or absence of chlorophyll can be no 

 sufficient reason for separating plants which are nearly related to one another 

 morphologically, and which agree in their structure and in their sexual organs, 

 where these are present. In Phanerogams the principle is thoroughly admitted. If 

 all flowering-plants which do not contain chlorophyll were formed into one class 

 in contradistinction to those which do contain it, the Rafflesiaceae, Balanophoreae, 

 Corallorhiza, Cuscuta, Orobanche, Monotropa, &c., would have, in spite of the 

 differences in their organic structure, to be combined into one class, and removed 

 from their true relationship. No one however disputes that Cuscula belongs to the 

 Convolvulaceae, Orobanche to the Labiatiflorae, Monotropa to the Pyrolaceae, and 

 Corallorhiza to the Orchideae. These affinities are inferred among Phanerogams 

 chiefly from the structure of the flowers and the embryo, and no one attaches the 

 least importance to the fact that the want of chlorophyll and the peculiar mode of life 

 of these plants gives them so different an appearance from that of their nearest allies. 

 It is one of the most beautiful results of a truly scientific morphology and classifica- 

 tion that, among Phanerogams, the remarkable habit of parasites and saprophytes is 

 regarded as an altogether secondary matter. But the same principle should also be 

 applied in determining the systematic relationships of Thallophytes ; habit and mode 

 of life, the presence or absence of chlorophyll should also be. treated as characters of 

 altogether subordinate importance, as it is a matter of subordinate importance in the 

 division of humankind into natural races, whether some support themselves by their 

 own industry, and others live by war and plunder. All Thallophytes which are 

 destitute of chlorophyll, i.e. all those which have hitherto been termed Fungi, must 

 necessarily agree with one another more or less in their habit and mode of life, 

 because they are all adapted to take up organised food-material containing carbon 

 from the substances on which they live. If they obtain this from living bodies, we 

 have parasitism developed in very various forms ; if they can make use of dead 

 organic remains, the habit and mode of life of the plant must vary accordingly. 

 Algae, in the sense in which the term has hitherto been used, are able to produce 

 carbonaceous food-materials out of carbon dioxide by assimilation ; they are not 

 therefore usually either parasites or saprophytes, but can maintain a more free and 

 independent life ; they are however compelled by the peculiarities of their organisa- 

 tion to live in water or in damp places : their dependence on assimilation requires 

 that they should inhabit localities where there is free access of light, while Fungi 

 are not absolutely dependent on light for their supply of food. 



