The structure & development of the mosses and ferns (Archegoniatae) . 173, A). This hasno chlorophyll, and as usual the large distinct nucleus isembedded in dense highly refractive cytoplasm. There arenext formed in the outer dome-shaped cell two or three walls,running more or less obliquely over the apex ; either at the topor at one side the last-formed wall encloses a small cell, whichis thrown off when the antheridium opens (Fig. 173, 0). Thisopercular cell, both in form and position, recalls strongly thatfound in the Marattiaceae. The divisions in the central cell correspond closely to tho
The structure & development of the mosses and ferns (Archegoniatae) . 173, A). This hasno chlorophyll, and as usual the large distinct nucleus isembedded in dense highly refractive cytoplasm. There arenext formed in the outer dome-shaped cell two or three walls,running more or less obliquely over the apex ; either at the topor at one side the last-formed wall encloses a small cell, whichis thrown off when the antheridium opens (Fig. 173, 0). Thisopercular cell, both in form and position, recalls strongly thatfound in the Marattiaceae. The divisions in the central cell correspond closely to those XI THE HOMOSPOROUS 345 in Ofioclea, but the number of sperm cells is larger, beingusually lOO or more. The development is also the same, andwill not be entered into here.^ After the final division of thesperm cells the nuclei remain slightly flattened in the plane ofdivision, as in the Hepaticae, and the mature spermatozoidsare coiled more flatly than in the Polypodiacea^. The freespermatozoid recalls that of Marattm or Eqitisetian rather than. Fig. 174.—A, Ripe antheridium of O. Claytoniana, just ready to open ; B, the same dischsperm cells, x6oo; C, two spermatozoids, X 1200. the Polypodiaceae. There are but about two complete coils,and the hinder one relatively larger than in the latter swimming there is peculiar undulating movement, suggestiveof the spermatozoid of Equisetuvi. The Ardiegoniuiii The archegonia are only borne upon the large heart-shapedprothallia, and occupy the sides of the projecting midrib, where, 1 Ior details see Campbell (12), p. 61. 346 MOSSES AND FERNS CHAP if the earlier ones are not fertilised, they may continue to formindefinitely ; but no correspondence can be made out betweenthem and the initial cells, and while formed for the most partin acropetal order, new ones may arise among the older ones. The mother cell of the
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