42 BOTANY AND PHARMACOGNOSY. 



Some of those used in medicine, are also used as foods on account 

 of the gelatinous carbohydrate lichenin which they contain. Be- 

 sides those given the following may be mentioned : Cladonia 

 rangiferina (reindeer moss), Lecanora esculenta (supposed to be 

 the manna of the Israelites. The Lichens are, however, chiefly 

 of interest because of the coloring principles which they contain. 

 Roccella tinctoria, Lecanora tartarea, and other species of Leca- 

 nora, yield upon fermentation the dyes orcein and litmus, the 

 latter of which finds such general use as an indicator in volu- 

 metric analysis. Cudbear, a purplish-red powder, is prepared by 

 treating the same lichens with ammonia water ; while in the prep- 

 aration of orchil, a purplish-red pasty mass, sulphuric acid and 

 salt are subsequently added. A number of species contain a yel- 

 low coloring principle, as Zeora sulphurea, Zeora sordida, Lecidea 

 geographica and Opegrapha epigcea. 



BACTERIA. 



The Bacteria, or Fission Fungi, occupy rather an anomalous 

 position, some writers -classifying them with Fungi and some 

 with Algae. They are i-celled plants, microscopic in size, and 

 of various shape. The contents consist of protoplasm and a 

 central body in some cases, which is looked upon as a rudimentary 

 nucleus. They are more or less colorless, but sometimes produce 

 a distinct pigment called bacteriopurpurin which is rose-red 

 or violet, and occasionally a chlorophyll-green color substance. 

 They are capable of multiplying by division in one, two, or three 

 directions, and under favorable conditions increase very rapidly 

 in number. The wall is more or less albuminous in character, in 

 this respect resembling the wall of the animal cell, and is provided 

 with one to many cilia, or flagella, the number and position of 

 which have been used as a basis of classification. Sometimes the 

 walls of the cells become mucilaginous, so that the bacteria hold 

 together forming a mass known as a zoogloea. Bacteria may form 

 resting spores which arise in two ways. In one case the contents 

 round off and take on a membrane forming a so-called endo- 

 SPORE ; in the other case the plant body is transformed directly 

 into a spore known as an arthrospore, as in some of the Blue- 



