THE DEHISCENCE OF THE ANTHER. 407 



some of the ovules to swell to a large, and occasion- 

 ally to a preposterous size, and become seed-like 

 masses without an embryo ; and the same circum- 

 stance, has been observed in Germany ; and, as it 

 can act so far, I do not see the impossibility of its 

 influencing the character of the seed when the 

 access of natural pollen is insufficient : and it seems 

 to me questionable whether some of the singular 

 varieties which occur among vegetables may not 

 have been so produced." 



Dr. Lindley states, that " Purkinje demonstrated 

 the correctness of Mirbel's opinion in 1808, that the 

 dehiscence, or bursting open of the walls of the 

 anther, which allows tlie grains to escape, is gov- 

 erned by hygrometrical causes ; or that the inner 

 lining of these walls is peculiarly sensitive to the 

 dryness and moisture of the atmosphere, as well as 

 the ripeness and dryness of the pollen ; that this 

 lining is of fibrous, cellular tissue, forming an in- 

 finite multitude of little springs," which by their 

 concentrated action open the valves of the anthers 

 when the pollen is ripe, and the atmosphere dry : 

 " so that the opening of the anthers is not a mere 

 act of chance, but the admirably contrived result of 

 the maturity of the pollen," when the surrounding 

 tissue, and of course this inner lining, has been ex- 

 hausted of its moisture by the developing pollen 

 grains. The observations of Mirbel confirm his 

 statement, for he found a great quantity of sap in 



