54 STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 



PLATE 16, continued: 



140. Transverse section of rachis near apex of a leaf with three pairs of pinna.' and 



a single initial cell, showing sectioning of marginal cells, m. 



141. Ditto; leaf with seventeen pairs of pinna?, growing by a group of marginal 



initials. 



142-143. Transverse section of rachis of a leaf with seven pairs of pinna:-, showing 

 cessation of division in marginal cells, m. Fig. 142 is between second 

 and third pairs of pinnae. < 360. 



144. Sagittal section of apex of a leaf with nine pairs of pinna-, and growing by a 



group of marginal initials, ;//. X 360. 



145. Horizontal section of tip of pinna; i, growing point. From a leaf with eleven 



pairs of pinnae. 



146. Transverse section of pinna near apex; ///, marginal cell. 



147. Transverse section of leaf through a developing pinna; /;/, marginal cell. From 



same leaf as fig. 146. 

 PLATE 17: 



148. Horizontal section of developing pinnule; lobes and sinus. 



141;. Horizontal section of teeth of pinnule lobe, with developing veinlets (shaded). 



150. Dorsiventral section of developing lamina. 



151. Transverse section of leaf with rudiment of sorus on margin; m, mother-cell of 



first sporangium; u, indusium. < 210. 



152. Outline of pinnule of unfolding leaf. X 42. 



153. Surface of pinnule shown in fig. 152: i, rudiment of stoma. 



154. Longitudinal section of young sporangium; central cell just formed. 



155. Transverse section of leaf-margin through a mature sorus; d, placenta; //, indu- 



sium. X 210. 



156. Oblique longitudinal section of developing sporangium with one central cell. 



157. Longitudinal section of young sporangium; stalk and wall segments cut off; 



cap not yet formed. : 360. 



158. Sagittal section of rudiment of sorus; ft, indusium; i, 2, successive sporangia. 



X 360. 



159-167. Sections of developing sporangia, showing stages as follows: Fig. 159, 

 first cleavage in mother-cell; d, placenta. Fig. 160, three-celled rudi- 

 ment. Fig. 161, first tapetal cell. Fig. 162, first tapetal layer com- 

 plete (on right), leaving the archesporial cell. A three-celled rudiment 

 at left. Fig. 163, division of the tapetal layer. Fig. 164, four arche- 

 sporial cells in equatorial-plate stage, dividing to make eight. Figs. 

 165, 166, adjacent sections of two-celled archesporium, dividing into 

 four. Fig. 167, spore mother-cells; tapetum degenerating. 

 PLATE 18: 



161-167. See above. 



168. Tetrads, with fragment of tapetum. 



169. Paraphysis arising from placenta. 



170. Sagittal section of sporangium, showing the spore mother -cells just before 



synapsis. 



171-172. Mature sporangia, from opposite sides. 

 173. Mature paraphysis. : 360. 

 174-175. Surface views of spores. 



176. Transverse section of stalk of sporangium. 



177. Germinating spore. : 360. 



178. Three-celled protonema, short type. 



179. Two-celled protonema. < 360. 



i So. Three-celled protonema, medium length. 



181. Four-celled protonema. 



182. Protonema with short basal cells. X 360. 



183. Six-celled protonema. 



184. Three-celled protonema. Long type. 



185. Five-celled protonema with two-sided initial. < 360. 



1 86. Base of a prothallus without protonema. 



187. Protonema with two segments from initial. 360. 

 iSS. Five-celled prothallus without protonema. < 360. 



