126 



GENERAL BIOLOGY 



only. No foot nor stalk appear ; only sporangium : and 

 in the sporangium, no sterile cells; only spores. 



The maximum development of sporophyte phase in the 

 bryophyte group of plants is found in the mosses, in which 

 the archegonia are terminal upQn a stem or branch, and, 



although produced in clus- 

 ters, but a single egg normally 

 develops to maturity. From 

 the fertilized egg there de- 

 velops a sporophyte of great 

 length which early ruptures 

 the archegonium wall, carry- 

 ing the upper end of it up 

 into view as the calyptra. 

 This falls away at maturity. 

 Foot, stalk and sporangium 

 are highly differentiated. 

 The foot is buried in the tis- 

 sues of the parent gameto- 

 phyte, whence it draws 

 nourishment for develop- 

 ment, as in the liverworts. 

 The stalk is long and pushes 

 the sporangium up conspicu- 

 ously into vicAv. The spo- 

 rangium is composed of a 

 number of highly diiferentia- 

 ted sterile parts. It contains 

 no elaters, and the spores 

 are situate in a cylindric layer surrounding a central core 

 of parenchyma cells (called the columella), and usually cover- 

 ed over by a detachable cap, the operculum, that grows be- 

 neath the calyptra and is a part of the sporangium itself. 

 Underneath the operculum there is often a peripheral 



Fig. 76. The moss sporophyte. A,C, F, 

 successive stages in its development; 

 c, calyptra (detached top of archego- 

 nium; X, foot; y, stalk; z, sporan- 

 gium; M, longitudinal section of the 

 sporangium ; o, operculum (detached) ; 

 /, columella; r, respiratory paren- 

 chyma; 5, spores; r, teeth; j^, breath- 

 ing pore (stomate), and the same 

 below in surface view. 



