Brown: Apogamy in Phegopteris polypodioides 27 



The first outgrowth, after forming an elongated flat structure 

 several cells in thickness and width, broadened into a prothallium 

 with a slight sinus. Tracheids formed in the thickened region 

 at the center. The second outgrowth continued its develop- 

 ment as an elongated, thick, club-shaped structure bearing 

 tracheids near the base. The third outgrowth at a very early 

 stage formed a slightly elongated prothallus-like structure, 

 distinctly notched and bearing a series of very short tracheids 

 in the elongated portion. 



On the very irregular prothallium shown in Fig. 1 1 a normal 

 embryo was formed near the base of the archegonial cushion, 

 while near the sinus an apogamous sporophyte developed. 

 This appeared as a cellular mass surrounded by proliferations, 

 from which the first leaf was formed. 



Of the apogamous outgrowths represented by Figs 12-20, 

 those of Figs. 12, 16-18, and 20 originated as cellular masses 

 on the archegonial cushion of the prothallia; those of Figs. 

 13-15 originated as lobes from the margins of the prothallia 

 and that of Fig. 19 as a lobe in the sinus. The cells in most of 

 these marginal lobes were large. The prothallium shown in 

 Fig. 13 was somewhat elongated and bore many lobes on the 

 margin of its apex. One of these lobes, after elongating into a 

 prothallus-like structure, several cells in width and one cell in 

 thickness, formed a cellular mass. From this were given off 

 three branches. The development of the apogamous outgrowth 

 was continued by a reversion to a broad thick prothallium with 

 a lobed apex. A series of tracheids were formed in the thickened 

 region of this outgrowth. All the branches given off by the 

 cellular mass were curled after the manner of a normal leaf, 

 in the early stages of their development, and one resembled 

 a normal leaf in shape. However, this was the extent of the 

 similarity between these branches and normal sporophytic 

 leaves. The branches were only one cell in thickness and no 

 tracheids were present. 



The apogamous outgrowth shown by Fig. 14 occurred as a 

 lobe on the margin of a very irregular and distinctly notched 

 proi:hallium, in the region of the sinus. From only a few cells in 

 wid:h the apogamous outgrowth developed into an elongated 

 prothallus-like structure, thickened in the center and branched 

 at its apex. One of these branches was narrow and several 



