344 HOFMEISTER, ON 



loosened and pushed aside by the developing germ-plant, 

 and ultimately dissolved.* The embryo in its first stages 

 appears surrounded by a tissue of very narrow cells (PL 

 XL VI, fig. 21). As early as during the occurrence of 

 the first divisions of the impregnated germinal vesicle, the 

 cells of the mouth of its archegonium die ; their fluid con- 

 tents become as clear as water, and their walls assume the 

 deep-brown colour so common in the dead cell-membranes 

 of vascular cryptogams. Similar changes sometimes occur 

 in those cells of the upper surface of the prothallium which 

 adjoin the mouth of the archegonium (PL XLVI, figs. 2J, 

 23). ^ ". ■ . 



It very rarely happens that more than one archegonium 

 of the same prothallium is impregnated. The rest wither ; 

 the contents of their central cells shrivel up into an irregu- 

 larly shaped ball of dark-brown matter, and all the cell- 

 membranes of the archegonium become brown. 



The' rudiment of the embryo when 4-celled grows to- 

 wards the middle point of the spherical prothallium by 

 repeated division of the cells turned away from the canal of 

 the archegonium. At the same time an active multiplica- 

 tion commences in the one lateral cell which occupies the 

 more pointed end of the oval embryo-rudiment. It elivides 

 by a vertical septum forming an acute angle with one of 

 the axes of the embryo. The outer of the newly-formed 

 cells is immediately divided again by a septum at right 

 angles to the last-formed septum. In the apical cell for 

 the time being of the excrescence (of the embryo) thus 

 produced, the division is repeated for a long time by septa 

 inclined alternately in two different directions (PL XLVI, 

 figs. 22, 23). This lateral shoot of the young rudimentary 

 plant — -which shoot up to a certain point is continually 

 elongating — is the first leaf. 



The cells of the second degree produced by the division 

 of the (primary) apical cell of the leaf, are divided by radial 

 longitudinal septa. Each of the tertiary cells divides — 



* Instances of this occur in the development, whilst within the prothallium, 

 of the germ-plant of ferns — in the penetration of the lower end of the moss- 

 fruit into the incipient vaginula — and in the displacement of the endosperm of 

 many phsenogams by the growing embryo. 



