Al.DniDGE ON POLLEN. 91 



the mostconvenient, or not unfrequently, at an appointed spot. 

 It now happens that a portion of the swollen fovilla is squirt- 

 ed out with a little explosion; this is produced by a double 

 cause : on the one part the fovilla is already swelled by the 

 water, and, on the other, the distended membrane is brought 

 together again by virtue of its own elasticity: under these 

 circumstances, the expelled fovilla presents itself under the 

 appearance of a long-drawn tubular (schlauch formige) mass, 

 and permits, in this particular situation, the nature of its mu- 

 cus to be sufficiently examined. [There appears, in this in- 

 stance, a discrepancy with the author's former statement, as 

 there is an inconsistency with fact. If the mucus swells like 

 Bassarine in water, why should it retain a cylindrical form in 

 this liquid? and I have always found that, except when the 

 fovilla was already coagulated by an acid, the mucus rapidly 

 diffused itself through water, and permitted the opaque par- 

 ticles to scatter themselves irregularly.] By the action of acids 

 the mucus is converted into a grayish tenacious mass, which 

 no longer scatters itself into flocks, but according to its kind, 

 appears, between two glass plates, in a long-drawn, cylin- 

 drical, continuous mass, from which the membrane either 

 doubles together, or along with which it becomes so obscure, 

 that treated in this way, its appearance may be regarded only 

 as an exception. [This description oidy applies to pollen that 

 dehisces by pores ; when the rupture takes place by a slit, the 

 form of the fovilla often remains unchanged.] 



In a dry situation, as when placed in free air, the pollen 

 becomes characterized by its mucus being tolerably trans- 

 parent ; but this transparency disappears when it is moisten- 

 ed with water. This circumstance, the author explains, with 

 Mohl, by supposing, that the dry mucus, and the little oil- 

 drops, possess by chance an uniform light-refracting power ; 

 and from thence it naturally results, that the fovilla, by 

 sucking up water, loses its transparency; this former unifor- 

 mity becoming destroyed. 



Besides the mucus, capable of being coloured yellow-brown 

 by iodine, the author has found, in some plants flowering in 



