PTERIDOPHYTES 



137 



FIGS. 309, 310. Archegonium of 

 Selaginella: 309, the neck and the axial 

 row (neck canal cell, ventral canal cell, 

 and egg); 310, fertilization, the sperm in 

 with the egg. After Miss 



spore walls are brought to the mega- 

 sporangia by the wind or by gravity. 

 The microspores drift among the 

 megaspores with protruding female 

 gametophytes bearing archegonia. 

 Then the sperms are discharged, 

 enter the archegonia, and fertiliza- 

 tion occurs (fig. 310). In these 

 female gametophytes, still in the 

 sporangia, the embryo sporophytes 

 develop and then emerge, a strobilus 



often being beset with young 

 sporelings. Later the strobilus 

 as a whole, with its attached 

 sporelings, drops off. 



Embryo. The embryo 

 (sporophyte) is developed 

 much as in Lycopodium (figs. 

 311-314). The suspensor (p. 

 130) is more extensive than 

 in Lycopodium, being of use 

 in relating the embryo to the 

 deep nutritive tissue within 

 the megaspore. The em- 

 bryonal cell at the end of the 

 suspensor first produces three 

 cells : a terminal cell that 

 develops the stem, flanked by 



to form the suspensor, the inner cell to form the *WO cdls (one on each side) 



embryo); 312, early stage of the embryo (at- that develop leaves. From 



tached to suspensor). the apical cell of the stem Qne Q thg j eaf segments tne 

 being evident; 313, later stage of the embryo, . 



showing (to the right) the apical cell of the stem foot 1S developed later (fig. 



between the apical cells of the first two leaves 313)) and Still later, from the 



and (to the left)- the developing foot; 314, an same segment the pr i ma ry 

 older embryo, showing the foot (to the right . f - ' 



below), the root (to the right above), the sus- root anses (% 314). When 



pensor, the two leaves (to the left) with their fully organized and emerging, 



ligules, the centrally placed stem tip, and the 

 developing vascular system extending between 

 stem and root tips. 311, after BRUCHMANN; 

 312-314, after PFEFFER. 



311 



FIGS. 3 : 3i4. - Embryo of Selaginella: 

 1, first division of fertilized egg (the outer cell 



the embryo resembles a seed- 

 ling dicotyledon escaping from 

 its seed. The tuberous foot 



