72 COMPOUND ORGANS OF PLANTS. 



93. The teeth of mosses are a -beautiful object beneath 

 the microscope, and follow a regular geometrical law in their 

 numerical relations, being either four, or multiples of that 

 simple number, 8, 16, 32, or 64; and from their absence, and 

 differfences in their number and degree of cohesion when 

 present, the generic character of mosses is whoUy taken. 



94. The teeth of mosses are exceedingly hygrometrical, or 

 easily affected by moisture. When the sun shines bright 

 and . warm, and the atmosphere is dry, the mosses on ten 

 thousand rooks and hills expand and spread abroad their 

 teeth, which may be seen then at right angles to the mouth 

 of their sporangia; the sunlight pours down into the spo- 

 rangia, and the young spores speedily .ripen under its influence. 

 But when clouds shade the sun, and the air becomes sur- 

 charged with moisture, the teeth of the peristome imme- 

 diately curve over the mouth of the sporangium, fitting 

 together in the most beautiful manner, and effectually closing 

 it, so that not one particle of moisture can enter the spo- 

 rangia to injure the young spores. This beautiful mechanism 

 may be seen in operation on the top of almost any stone wall, 

 or on the surface of rooks, in the winter months, by those 

 who will only search for it. 



95. However philosophers may attempt to explain these 

 movements on mechanical principles, and it is probable that, 

 with the progress of science, all vital phenomena will be 

 ultimately resolved into physical laws, yet have we not in 

 these phenomena the first faint foreshadowings, as it were, of 

 the powers of a higher vitality? Is there not manifest a 

 shrinking away of the young life of mosses from what would 



