620 THE SUBDIVISIOXS OF THE VEGETABLE KINGDOM. 



the verticillate Siphonete, Braparnaldia, many of the Brown Sea-weeds) which 

 do show a distinction between axis and appendages, though the distinction is not 

 usually so marked as that between the stem and leaves of a higher plant. Simi- 

 larly, though for the most part possessing a relatively low organization, some 

 Thallophytes (especially the higher Fungi and certain of the Brown Sea-weeds) 

 show considerable differentiation of structure. The Thallophyta consist of many 

 divergent and more or less sharply characterized groups. These include the Green 

 Algse {Ghlorophyeece, which includes the alliances Protococcoideae, SiphonesB, Con- 

 fervoideae, Conjugate, and Chai-ales), the Brown Sea-weeds (Phceophycece), the Eed 

 Sea-weeds {Rhodophycece or Floridece), the Blue-green Algce {Cyanophycece or 

 Schizophycece), the Bacteria {Schizomycetes, here included with the last-named 

 group in one class, the Schizophyta), the Diatoms {Bacillariales), and the Fungi. 

 Some Botanists consider that the Myxomycetes (or Mycefozoa), and the Dino- 

 flagellata {Peridinece) are also plants. These last groups are almost certainly 

 branches of the Protozoa; and though possessing certain plant-like characters (as 

 indicated above), they show no near affinity with other plant groups. Whether 

 they should be considered as plants or animals must therefore remain a matter of 

 opinion. 



The same may be said of certain other organisms regarded by zoologists as 

 Flagellate Protozoa, but showing undoubted affinities with the lower forms of 

 Green Algae. There exists, in fact, an unbroken series of forms, connecting un- 

 doubted Protozoa, having mouths by which they eat solid food, with undoubted 

 green plants depending entirely on soluble inorganic food. The dividing line 

 between animals and plants is here obviously an artificial one, and is naturally 

 drawn by different authorities at different points in the series. 



The name Thallophyta, then, is given to all plant-forms below a certain grade 

 of organization, and includes many separate and widely divergent lines of descent. 

 The Thallophj' tes may be pictured as the shrubby growth around the base of the 

 phylogenetic tree representing the plant kingdom. The lower part of the main 

 trunk of the tree, that is to say, the line of descent by which the higher plants 

 have originated, is probably represented by certain of the Green Algse. 



Qass I.— SCHIZOPHYTA. 



For the most part exceedingly small organisms, which propagate entirely by 

 asexual methods. They consist of isolated cells, cell-filaments, surfaces, or masses. 

 Though till recently regarded as without nuclei, these bodies have been found in a 

 number of forms, and this view is being abandoned. They include both coloured 

 and colourless forms; but the coloured forms never exhibit pure chlorophyll. 



