Physiology of the Gyropodium coccineum. 59 



There is a mechanism worthy of notice in the construc- 

 tion of the valves. It was necessary ihrt these should 

 close in such a manner as effectually to exclude moisture, 

 since this would destroy the seeds, or prevent them from 

 being thrown out of their receptacle. A single valve, form- 

 ing a part of the sphere containing the powder, would hard- 

 ly afford sufficient security in this respect ; and the hinge 

 would not possess strength and elasticity enough, to cause 

 the valve to shut down close after several successive open- 

 ings. The same difficulty would exist, had two valves been 

 so placed on the top of the fungus as to close against each 

 other, like the jaws of an animal. 



But there was another object to be effected, which could 

 not be attained simply by a double valve of the kind last 

 mentioned. It was necessary that the opening for the es- 

 cape of the powder should be of considerable magnitude, 

 and the nearer it should approach the circular form, it is 

 obvious, the greater would be the facilities for this process: 

 and two valves, closing against each other, could not pro- 

 duce such an aperture. But as the valves to this fungus 

 are actually constructed, they not only secure the contents 

 of the inner sack from the access of moisture, but on open- 

 ing present an aperture of a polygonal form. At F, on 

 the plate, is a view of three sets of valves, taken from three 

 specimens ; the eye being placed directly above the centre 

 of the plant, and looking down upon the edges of the 

 valves when closed. It will be seen that these valves are 

 all somewhat irregularly curved outwards, so that their 

 convex sides are brought into contact ; and yet they are so 

 fitted to one another, that there is no interstice between 

 them, when closed. This construction will also render the 

 aperture somewhat polygonal, when the valves open ; or 

 rather it v/ill be a spherical polygon. By this construc- 

 tion too, if I mistake not, a greater degree of strength and 

 elasticity, will be imparted to the valves : for from their 

 centre, or greatest height above the surface of the sphere 

 constituting the head of the fungus, there is a gradualslope 

 towards their extremities ; which, as already remarked, 

 curve outwards ; and hence when they are pressed asunder, 

 it is not merely on a line connecting those extremities that 

 they yield, but also along all that part of the envelope be- 

 tween this line and the curve of the valve, and likewise in 

 the valves themselves along their slopes. Are there not 



