214 AOOTYLEDONS LICHENS ALG.E DIAGRAM 18 



with time. They are generally of a grey colour, and sotnetimes 

 grow on the trunks of trees, and sometimes on walls and slates. 

 They require very little moisture. Some lichens appear like 

 large pendant filaments, which sometimes cover over fir-trees, 

 and finally destroy them. 



FAMILY OF ALG^E. 



The family of algee includes, firstly, the green filaments which 

 are found in stagnant waters, and secondly, the marine plants, 

 which are sometimes of a beautiful green, and sometimes of a 

 brown or red ; they cover the rocks, and it is a pleasant amuse- 

 ment to collect and dry them. But they must be allowed to lie 

 for some time in fresh water, till all the salt which they contain 

 has been washed out, or else they will not dry. 



The marine algse, or seaweeds, are useful for many purposes ; 

 firstly, they form an excellent manure when collected and spread 

 upon the land ; and secondly, soda, iodine, and other chemicals 

 which are very useful in manufactures and medicine are pro- 

 cured from them. Soda is obtained by drying seaweeds in 

 large heaps, and then burning them and washing the ashes. 

 The water dissolves the soda, and on evaporation, the soda is 

 deposited in crystals. 



Some species of seaweeds are used for food, such as the dulse, 

 which is eaten boiled, as a kind of vegetable, and the Carrageen 

 Moss which is used to make a kind of jelly. 



The longest of ail known plants are seaweeds ; and one species 

 which abounds in the Antarctic seas is said to grow to the enor- 

 mous length of 600 feet. 



