Browx: Regeneratioij in Phegopteris polypodioides 393 



the soil cultures became appressed to the soil as a result of acci- 

 dents in watering. 



Only one case of regeneration was obtained, although a large 

 number of leaves were experimented with. Regeneration began 

 in about six weeks after the leaf had been removed from the sporo- 

 phyte and laid on sand moistened with Knop's full nutrient solu- 

 tion. One side of the petiole, near its base, was destroyed by 

 decay, and a short distance above this point on the opposite side 

 of the petiole a slight swelling occurred, from which a cellular mass 

 developed. At first it was slightly elongated. Fig. i, afterwards 

 it became much thickened and broadened, Fig. 2, and finally as- 

 sumed the shape shown in Fig. 3. From this cellular mass there 

 developed two intermediate structures between leaves and pro- 

 thallia, then rhizoids and four normal leaves. Neither a true root 

 nor a stem "Anlage" was formed. 



The first of the intermediate structures resembled a very much 

 elongated prothallium, one cell in thickness, with an expanded 

 heart-shaped apex. Tracheids arranged in rows resembling a true 

 midrib extended up through the portion of the structure corres- 

 ponding to the petiole into the expanded or blade-like part. Here 

 the rows of tracheids branched dichotomously one branch going 

 to each lobe (Figs, i and 2). The margins of both the elongated 

 and expanded regions were for the most part smooth, with the 

 exception of two papillae, one of which developed on the elongated 

 and one on the expanded part. 



The second intermediate structure which developed from the 

 cellular mass was even more thalloid in form and structure than 

 the first one. Both the elongated and broadened portions like 

 those of the first were only one cell in thickness. The expanded 

 portion differed somewhat in appearance as it was not so distinctly 

 heart-shaped and its margin bore many more papillae. There 

 were no indications of tracheids present in either of the portions 

 representing petiole or blade. 



Growth was rapid and apparently normal in both of these in- 

 termediate structures, but the second one never attained the size 

 of the first. Neither was long-lived, death occurring soon after 

 the normal leaves began to develop. The rhizoids resembled in 

 every way those of a normal fern gametophyte. They formed from 



