BOTANY AND PHARMACOGNOSY. 



THALLOPHYTES. 



The Thalloph3M:es include the lowest orders of plants, — 

 i.e., those simplest in form and structure. They are supposed also 

 to represent more or less primitive types. In these plants the 

 plant body does not show a differentiation into root, stem and 

 leaf, as in the higher plants,, and is termed a thallus. The 

 thallus may branch in various ways, but the structure remains 

 more or less uniform throughout. It should be understood, how- 

 ever, that even in this group of plants certain cells or groups of 

 cells miay become specialized, i.e., set apart for a particular func- 

 tion, as, for example, the reprtpductive cells. The Thallophytes 

 vary in size and general appearance from minute unicellular 

 organisms and those which'are filanientous and delicately branched 

 tp large leaf-like organisms many feet in length (Figs. 6, 9, 13). 



The Thallophytes are divided into the two groups of plants 

 known as (i) Algae and (2) Fungi. The Algae produce chloro- 

 plasts, and hence are capable of manufacturing food from the 

 inorganic substances air and water (see page 108), which fact 

 constitute^ a fundamental difference between them and the Fungi. 



ALG^. 



Algae are also characterized by their habit of living in water 

 or in moist places, and they are sometimes classified as " fresh 

 water algae " and " salt water algae " (Fig. 9). In the first group 

 are included the common pond-scums and certain forms living 

 on trees, i;npist ropks, fences and elsewhere, and in the second 

 group the sea-wepds. .; 



In jaddition to the chlorophyll (see page 159) of th^ chloro- 

 plasty other color substances are fpynd in Algae, which mask the 

 greencolo^ fp a ponsiderable extent.' On the basis of their color 

 Algap are subdivided into (i) Blue-green Algae or Cyanpphyceae, 

 (2) Green Algae or Chlprophyceae, (3) Brown Alg^ or Phaeo- 

 phyceae, and (4) Red Algae or Rhocjophyceae. While no attempt 

 will be made to consider these groups in ;detail, it should be 

 stated that they not only vary in color, but they aisp vary greatly 

 in structure and general appearance. A few type ^orms, will be 

 considered in order to illustrate their habits of life. 



