MEPATtGM 



347 



by the rapid growth of the surrounding tissue of the thallus 

 {A, B, and C, 

 Fig. 333). In 

 other cases the 

 antheridia are de- 

 veloped in great 

 numbers upon 

 special branches, 

 as in Marchantia, 

 which has a large 

 " antheridial disc" 

 {A and B, Pig. 

 331, Jiu), in whose 

 upper surface are 

 to be found many 

 imbedded anther- 

 idia. That the an- 

 theridia are actu- 

 ally external in 

 this case also, be- 

 coming apparent- 

 ly internal by the 

 growing up of the 

 surrounding tis- 

 sues, is well shown 

 in Fig. 333. In 

 still other cases 

 {e.g., in Junger- 

 'm.anniacem) the 

 antheridia are in 

 the axils of the 

 leaves, and occur 

 singly or in groups. 

 453.— The ar- 

 chegonium first 

 appears as a simple 

 papilla, composed 

 of a single cell, 

 which, by subdi- 

 vision in vajdous 



Fig. 235. — The archegonia, and origin of the eporogo- 

 nium oiMarehantla polymorjjha. I. and //., young arche- 



fonia ; e, germ cell ; at, lowest cell of axial row of cells. 

 11. and /F., the same after the formation of a central 

 canal by the absorption of the axial row of cells in the 

 neck. v.. the same when mature and ready for fertiliza- 

 tion. F/., the base of a fertilized archegonium, the 

 germ-cell,/, divided into two cells by a diagonal partition, 

 VII., later stage of the same, ahowmg further division of 

 the germ-cell, /. and the beginning of the growth of a 

 perianth, pp. VIII., still later stage of the same, the 

 perianth, pp, now enclosing the archegonium ; x, the 

 withered neck of the archegonium. IX., tne unripe sporo- 

 gonium, enclosed in the old waJls of the archegonium, 

 now called the calyptra, a ; f, wall of sporogoniura ; 

 St, the short, undeveloped stalk of the sporogoninm. 

 Inside of the sporogonium are the young elaters arrange 1 

 radially, and between them are the spores. /. to VIII. 

 X 300 ; IX. about 30.— Alter Sachs. 



directions, gives rise to a more or less 



