. The structure and development of mosses and ferns (Archegoniatae). sperm cell, after its finaldivision, shows no nucleolus. The first sign of the formationof the spermatozoid that could be detected was an indentationupon one side, followed by a rapid flattening and growth of thewhole nucleus. The cytoplasmic prominence which, accordingto Strasburger, is the first indication of the formation of thespermatozoid, could not be certainly detected. The main partof the spermatozoid, stains strongly with alum-cochineal, andis sharply differentiated against the colourless cytoplasm, and VIII MARATTIA
. The structure and development of mosses and ferns (Archegoniatae). sperm cell, after its finaldivision, shows no nucleolus. The first sign of the formationof the spermatozoid that could be detected was an indentationupon one side, followed by a rapid flattening and growth of thewhole nucleus. The cytoplasmic prominence which, accordingto Strasburger, is the first indication of the formation of thespermatozoid, could not be certainly detected. The main partof the spermatozoid, stains strongly with alum-cochineal, andis sharply differentiated against the colourless cytoplasm, and VIII MARATTIALES 279 for some time shows the characteristic nuclear structure. Theorigin of the ciha was not clearly made out, but there is littlequestion that they arise from a blepharoplast as in (jther casesthat have been more recently investigated. The free sperma-tozoid (Fig. 152, I), is a flattened band, somewhat blunt behindand tapering to a fine point in front; attached to a point justback of the apex are several fine cilia. The body shows onlyabout two complete Fig. 152.—Marattia DouglasU. Development of the antheridium. A-D, Longitudinalsection, X515; E-G, surface views, X257; H, ripe sperm cells; I, free spermato-zoids, X1030; 0, operculum. The youngest archegonia are met w^ith some distance backof the growing point, and apparently any superficial cell ispotentially an archegonium mother cell. The latter dividesusually into three superimposed cells (Fig. 153, A), of whichthe lowest (b) forms the base of the archegonium. The basalcell, however, may be absent in Marattia Douglasii, as is alsothe case in Angiopteris and Dancea. From the middle cell by atransverse division are formed the primary neck canal cell and 280 MOSSES AND FERNS CHAP. the central cell. Each of these divides again transversely. Inthe upper one this division is often incomplete and confined tothe nucleus; but in the central cell the division results in theseparation of the ventral canal cell from the o
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
