THE BRACKEN FERN. !)1 



PLATE XXII. 



THE BBACKEN FERN. THE LEAF, EEPEODUCTIVE OKGANS, AND DEVELOPMENT. 

 FIG. I. Portions of the saute leaf, seen from beneath, x 2. 



FIG. II. Section across the plane a-b. of one pinnule of the above. D. 2. 

 The chlorophyll-bearing cells are alone shaded. 



FIG. III. Similar section across the margin of a sterile leaf. D. 2. 



FIG. IV. A similar section across the margin of a spore-bearing leaf. D. 2. 



FIG. V. A young sporangium from the above, in optical section. 



FIG. VI. A ripe sporangium from the same. Surface view. 



FIG. VII. A similar sporangium after rupture under pressure. 



The right hand portion of the figure, indicated in outline, represents the result of 

 rupture under imbibition of water. 



(Figs. V. to VII. D. 3.) 



FIGS. VIII., IX., X. Early stages in the germination of a fern-spore, grown on a slab 

 of limestone in a warm damp atmosphere. (The outside of a flower pot answers very 

 well). D. 4. 



No trace of chlorophyll was yet visible. 



FIG. XI. A later stage of the same. 



The developing prothallus, now quite green, was growing from an apical cell, up. 

 i. to iii. indicate the last formed cells of the apex. (Compare Figs. XX. und XXI. of 

 Plate XXI.) D. 4. \ p.c. osrnic acid. 



FIG. XII. One cell of Fig. XI. in detail, viewed in optical section. F. 2. 



FIG. XIII. A sexually mature prothallus, viewed from beneath. 



The archegonia are indicated in black, and the antheridia are left white, x 10. 



FIG. XIV. A portion of the same near the edge of the cushion, highly magnified. 

 The antheridia are drawn focussed to the level of the dividing central eel's, and the 

 detailed structure of the investing cells of both archegonia and antheridia is omitted. 



FIG. XV. An older antheridium. 



