PIN JUS AND THIS IB KIN 309 



has become imbedded in the wood of the branch, 

 and it evidently cannot plant its seeds until the 

 limb decays. It is a question if the seeds will 

 then be viable. 



375a. Do cones which, like Figs. 323 and 324, never open, 

 contain good seeds, the same as other cones do ? Let the pupil 

 watch the effect of scorching by fire in opening cones. 



Fig. 323. 

 Cone of spruce pine. 



376. We have now discerned two most impor- 

 tant characters in plants, — the fact that some plants 

 bear their ovules (and seeds) in a closed receptacle 

 or ovary, whereas others bear naked seeds. These 

 characters enable us to divide all flowering plants 

 into two great classes, the angiosperms and the 

 gymnosperms. The angiosperms, or those having a 

 pericarp, comprise the greater part of our com- 

 mon plants, nearly all those, in fact, which we 

 have studied up to this point. The gymnosperms, 



