IV 



THE JUNGERMANNIACE^ 



85 



made parallel to the surface of a male branch. The apex is 

 occupied by an apical cell of the usual form, and the cell divisions 

 in the young segment are extremely regular. The segment first 

 divides into an inner and an outer cell, and the former probably 

 next into a dorsal and a ventral one. The dorsal cell divides 

 by a longitudinal wall into two nearly equal cells, of which the 

 inner one, dividing by a wall perpendicular to the first, gives 

 rise to the primary cell of the antheridium (Fig. 35, Ac?). 

 This cell now projects above the surface of the thallus, and 



Fig. 35. — Aneura pinnati/ida(J>ie&i). A, Horizontal section of the apex of a young antheridial branch, 

 X565; .r, the apical cell; $, antheridia ; B, transverse section of a young archegonial branch, 

 passing through the apical cell (,i-) ; ?, young archegonia, X525; C, longitudinal section of a 

 nearly ripe archegonium, X262; D, E, spermatozoids a^ P cilia calycina, X1225 (D, E, after 

 Guignard). 



divides into a single stalk cell, which undergoes no further 

 divisions, and the antheridium mother cell. The divisions in the 

 latter correspond to those in the other Jungermanniaceae. First 

 a vertical wall is formed, dividing the young antheridium into 

 two equal parts. Next, in each of these, two walls arise, inter- 

 secting each other as well as the median wall, and dividing 

 each half of the antheridium into three cells, two peripheral 

 ones and a central one. (A somewhat later stage than this is 

 shown in Fig. 35, A.) The peripheral cells do not reach to 



