THE AMERICAN BOTANIST 



109 



of the fact that when a watery solution becomes sohd, the ma- 

 terials composing it tend to separate, and have proposed to re- 

 duce the amount of water in grape juice by freezing. In freez- 

 ing, the water turns to ice, leaving the sugar and other ingred- 

 ients as a thick syrup. By this means a gallon of grape juice 

 may be reduced to a quart and at the same time the flavor is not 

 afYected. In freezing, also, much of the acid crystallizes out, 

 making the juice less sour and removing the rough taste often 

 encountered in fruit juices. The method of course, is not 

 new. Every boy in the maple sugar regions is aware that if 

 maple sap be allowed to freeze and the layer of ice at the top 

 be removed, the remainder will be much sweeter. In a similar 

 way, vinegar and other liquids containing water may be con- 

 densed. 



Nature of Lichens. — Almost everybody has a general 

 idea of what lichens are. They are recognized as the gray- 

 ish-green patches found on the ground, on rocks and on the 

 trunks of trees, fences and the like. Sometimes as in the case 

 of the reindeer moss (Cladoma) and the bearded moss (Us- 

 nea) the plant body or thallus may assume a branching form, 

 though usually it forms a crust-like growth over the object to 

 which it is attached. Lichens are usually found in moist sit- 

 uations or at least in places where the air is moist for a part of 

 the time. They have always been a puzzle to the systematic 

 botanist. They are known to be composed of an alga and a 

 fungus in a sort of partnership, but because they have a recog- 

 nizable form, some botanists suggest classing them as a separ- 

 ate group of plants. This view of the matter has prevailed 

 until recently, but the tendency now is toi class them with the 

 fungi to which they are related. The fungus in the associa- 

 tion, it now appears, is not exactly a partner; it is more like 

 a slave-holder that required the algae to work for it. The 

 alga seems only accidentally a member of the lichen community 

 for elsewhere it lives a free existence. Even when removed 



