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 pinnae and 



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



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



initials. 



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

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

 and third pairs of pinnae. X 360. 



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



group of marginal initials, m. X 360. 



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



pairs of pinnae. 



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



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



same leaf as fig. 146. 

 PLATE 17: 



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



149. 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. X 210. 



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



153. Surface of pinnule shown in fig. 152: /#, 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; u, 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. X 360. 



158. Sagittal section of rudiment of sorus; u, 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. X 360. 

 174-175. Surface views of spores. 



176. Transverse section of stalk of sporangium. 



177. Germinating spore. X 360. 



178. Three-celled protonema, short type. 



179. Two-celled protonema. X 360. 



180. 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. X 360. 



186. Base of a prothallus without protonema. 



187. Protonema with two segments from initial. X 360. 



188. Five-celled prothallus without protonema. X 360. 



