. The structure and development of mosses and ferns (Archegoniatae). two similar initials,X, X, X560; B, longitudinal section of an advanced prothallium of O. cinnamomea,X260; C, horizontal section of a similar one, showing two initials, X260. The prothallia are long lived if they remain unfertilised,and Goebel ((i6), p. 199) states that in O. regalis they mayreach a length of four centimetres. He also records a genuinedichotomy of the older prothallia of this species. The Antheridium f Under favourable circumstances the first antheridia appearafter about a month in O. Claytotiiana, and contin
. The structure and development of mosses and ferns (Archegoniatae). two similar initials,X, X, X560; B, longitudinal section of an advanced prothallium of O. cinnamomea,X260; C, horizontal section of a similar one, showing two initials, X260. The prothallia are long lived if they remain unfertilised,and Goebel ((i6), p. 199) states that in O. regalis they mayreach a length of four centimetres. He also records a genuinedichotomy of the older prothallia of this species. The Antheridium f Under favourable circumstances the first antheridia appearafter about a month in O. Claytotiiana, and continue to form THE HOMOSPOROUS LEPTOSPORANGIATAi 351 for a year or more. In O. cinnamomea they first appearedabout two weeks later. While they are almost always presentupon the large female prothallia/ numerous exclusively maleplants are always met with. These latter are usually irregularin form, and even filamentous, especially when crowded. Uponthe latter the antheridia are either terminal or marginal; in theflattened prothallia they occur mainly upon the margin and. Fig. 194.—A, Prothallium of O. Claytoniana, about two months old, X about 30; B,base of an older prothallium of the same species with a secondary prothalliumipr^) growing from it, X8o; ^, antheridia; C, small branching male prothalliumof the same species, X7S. lower surface of the wrings. The development correspondsclosely in all forms that have been examined, and differs con-siderably from that of the Polypodiace^e. The mother cell is cut off as usual, but the second wall isnot funnel-shaped, but plane and inclined, so that it strikes thebasal cell. In the larger of the two cells thus formed a vary- * Luerssen (/. c. p. 449) states that they are often absent from very vig-orous prothallia.^ 352 MOSSES AND FERNS CHAP. ing number of divisions occur, cutting off a series of lateralsegments, much after the fashion of a three-sided apical segments thus cut off form the basal part of the anther-idium, and when
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