296 



Introduction to Botany. 



constitution of the nu 



Fig. 158. 



Diagrams of the sporophyte 

 and gametophyte of a moss. 

 The spore n produced asexu- 

 ally in the capsule m (which 

 with its stallc / is the sporo- 

 phyte) is the beginning of 

 the gametophyte. All of the 

 gametophyte produced by 

 the germination of the spore 

 is shaded ; all of the sporo- 

 phyte is left unshaded, p in 

 ^, the protonema from which 

 springs the moss plant g 

 (gametophyte together with 

 p) , bearing an archegonium 

 {s) with its egg, and an an- 

 theridium(?')with its sperms. 

 B, a later stage, the capsule 

 or sporophyte having sprung 

 from the fertilized egg. 



cleus of the fertilized egg is doubled 

 by this union, so that the fertilized 

 egg contains the same number of 

 chromosomes as do the nuclei of 

 the cells which make up the body 

 of the fern plant or sporophyte 

 springing from the fertilized egg. 

 Therefore we look upon the ferti- 

 lized egg as the one-celled stage 

 of the sporophyte. 



When the moss spore (Fig. 158, 

 ii) germinates, a multicellular body 

 is produced (protonema, p') from 

 which springs the moss plant (^g) 

 bearing antheridia (r) and arche- 

 gonia (i-) at its summit. Evidently, 

 therefore, the entire body resulting 

 from the germination of the spore 

 is the gametophyte. The egg after 

 fertilization produces the slender 

 stalk (/) and capsule {ni), namely, 

 all of the unshaded part of Fig. 

 158, B, which must be the sporo- 

 phyte, since it is produced in the 

 same manner (namely, from the 

 fertilized egg within the archego- 

 nium) and has the same position 

 in the life cycle as has the fern 

 plant in the life cycle of the fern. 

 It is true that the stalk and capsule 

 appear to be an organic part of the 

 moss plant, but from the evidence 

 before us we must conclude that 



