Brown: Apogamy in Phegopteris polypodioides 25 



In the experiments of the second year apogamous outgrowths 

 were first observed in the laboratory cultures on Knop's full 

 solution about four to six months after sowing. Subsequently 

 they developed in essentially all the cultures. These outgrowths 

 were very diversified in form, and while some originated as 

 cellular masses, at various places on the archegonial cushion, 

 the majority developed as outgrowths of the prothallia in the 

 region where the sinus usually occurs. It was only in rare cases 

 that sexual organs, either antheridia or archegonia, formed on 

 the prothallia bearing apogamous outgrowths. 



Fig. 7 shows an apparently normal and slightly elongated pro- 

 thallium with a broad lobed apex. No sexual organs developed, 

 although a well-developed archegonial cushion was present. 

 From the region of the sinus a lobe formed. Narrow at first, it 

 gradually widened and then branched to form two prothallia 

 with broad apices, each having a sinus. In the thickened 

 central region of each of these branch-prothallia a cluster of 

 tracheids appeared. In the meantime, from the center of the 

 archegonial cushion of the original pro thallium a cellular mass 

 began to form. This continued to grow as a thick conical mass. 



The apogamous outgrowth shown in Fig. 8 formed as a 

 lobe from the sinus of a very irregular, elongated prothallium 

 whose apex was lobed. This lobe, which later became an apog- 

 amous sporophyte, was at first one cell in thickness and several 

 cells in width. It broadened and thickened into a bulbous 

 cellular mass, then elongated and formed a series of tracheids 

 in the center. Finally it reverted to a filament one cell in thick- 

 ness. 



Fig. 9 shows an apogamous outgrowth which originated as 

 a lobe from the irregular apex, a little to one side of the center 

 of an elongated prothallium. This lobe broadened and thickened, 

 forming two branches. One branch did not develop as rapidly 

 as the other and appeared more thallus-like, being only one 

 cell in thickness. The other branch, after elongating slightly, 

 broadened into a prothallium thickened at the center and with 

 a heart-shaped apex. Tracheids formed in this thickened area 

 and a small branch developed at one side of the prothallium 

 near the apex. 



The apogamous sporophyte shown in Fig. 10 developed 

 first as a cellular mass on the meristem near the sinus of a very 



