Some Questions which they Suggest. 53 



cases Nature seems not to ask herself what is the single 

 best way of using the instruments at command, but, given 

 certain organs, how to attain the end in view with the 

 greatest amount of variation ! 



THE OPENING OF THE SPOKANGIA. In some cases, as 

 already mentioned, the sporangium opens by an indetermi- 

 nate rupture, in other cases Nature differentiates it into 

 two parts, the upper forming sometimes a lid, as in 

 Craterium, sometimes falling away early, as in Arcyria. 

 Just the same kind of difference prevails, it will be 

 remembered, in the mosses, the sporangia of the clay 

 mosses (Phascum) opening by a decay of their sides, the 

 sporangia of most of the mosses on the other hand having a 

 regular dehiscence. 



It is a beautiful sight to see through a microscope the 

 opening of a sporangium of a myxie under the warmth of the 

 sun. We have watched it in the Trichia fallax; sometimes 

 there appears a small hole in the membrane towards the 

 top, which enlarges into a chasm ; sometimes the whole 

 upper part seems lifted or pushed up. Then the closely- 

 packed spores begin to start out one after the other 

 falling at varying distances; then the whole surface of the 

 mass of spores and elaters begins gently to heave and 

 move, and the elaters sway about like the arms of a polype. 

 These actions are, we presume, due partly to the elasticity 

 of the hairs seeking to expand in every direction, and partly 

 to the unequal thickness of the parts of the elaters and 

 the consequently unequal action of the heat on the elaters 



