. The structure and development of mosses and ferns (Archegoniatae). St. Fig. 189.—Polypodium falcatutn. A, Cross-section of a sterile leaf, cutting across oneof the smaller veins, X260; st, section of a stoma; B, similar section of a sporo-phyll, showing the position of the sorus above the vein, X85. way, but are not all developed at the same time, so that a singlesorus may contain nearly all stages of development. The spo-rangium here can be readily traced back to a single epidermalcell. The sporangial cell protrudes until it is nearly hemispher-ical, when it is cut off by a wall level w
. The structure and development of mosses and ferns (Archegoniatae). St. Fig. 189.—Polypodium falcatutn. A, Cross-section of a sterile leaf, cutting across oneof the smaller veins, X260; st, section of a stoma; B, similar section of a sporo-phyll, showing the position of the sorus above the vein, X85. way, but are not all developed at the same time, so that a singlesorus may contain nearly all stages of development. The spo-rangium here can be readily traced back to a single epidermalcell. The sporangial cell protrudes until it is nearly hemispher-ical, when it is cut off by a wall level with the surface of the s IX FILICINEAl LEPTOSPORANGIATjE 341 placenta. The basal cell takes no further part in the develop-ment of the sporangium, and after a time becomes indistin-guishable. The outer cell now divides by a wall, occasionallytransverse, but much more commonly strongly inclined (, A), and striking the basal wall. This is now followed bytwo others, also inclined, and meeting so as to enclose a pyram-idal apical cell, from which a varying number of
Size: 2303px × 1085px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
