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 u-pcm 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 



17 \ W-vrM ing the upper end of & U P 



Y IrO^I into view as the 



BI-PY, * This falls away at 



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- 



M 



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

 successive stages in its development; 

 c, calyptra (detached top of archego- 

 nium; x, foot; y, stalk; 2, sporan- 

 gium; M, longitudinal section of the 



ously into view. The spo- 

 rangium is composed of a 



rSfflSSB;' 1 ?S3SS?t!S2: number of highly differentia- 



chyma; s, spores; t, teeth; , breath- f P /| cfprilp nprt<5 

 ing pore (stomate), and the same 16 partS. 



below in surface view. 



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 



