CHARACE& 



179 



The Characese are either monoecious or dioecious. In the former 

 case the male and female organs are formed in close juxtaposition on the 

 same node, the archegone being somewhat below the antherid in Nitella, 

 above it or by its side in Chara. The archegones, like the antherids, are 

 metamorphosed leaves. When ready for fertilisation, the archegone has 

 a longer or shorter ovoid form, and is borne on a short pedicel-cell. In 

 the interior is an axial row of cells enveloped by five tubes, which are at 

 first straight, but are afterwards coiled spirally round the axial row. 

 The lowest portion of each of these tubes is an elongated unsegmented 

 cell; while at the upper part 

 one or two very small cells are 

 segmented off. In Nitella each 

 of the terminal cells again di- 

 viides into two by a vertical 

 septum. The five terminal cells 

 of Chara and the ten terminal 

 cells of Nitella are not twisted, 

 and form together the crown. 

 When the archegone is ready 

 for impregnation these crown- 

 cells separate from one another, 

 forming the neck, and leaving an 

 open passage down to the axial 

 row. This apical cavity is, how- 

 ever, very nearly closed below 

 by a diaphragm formed by the 

 projecting inwards of the five 

 neck-cells, through which there 

 is only a very narrow opening 

 for the entrance of the anther- 

 ozoids. The apical cell of the 

 axial row is much larger than 

 the rest, and is the female or 

 germ-cell, corresponding to the 

 central cell in the archegone 



of the higher Cryptogams. It is filled with protoplasm, oil-drops, and 

 starch-grains ; its apical portion, the apical papilla, or receptive spot, 

 containing only hyaline protoplasm. Between the apical cell and the 

 pedicel-cell of the archegone, there is in Chara only a single cell, in 

 Nitella a group of cells, the ' Wendungszellen.' Before fertilisation the 

 crown is a compact structure covering the apical cavity ; but when the 

 archegone is ready for impregnation a small aperture is formed in its 



FIG. 165. A, fertile branch ot Nitella. flexilis 

 (natural size) ; /, internode ; b, branches. B, upper 

 portion of fertile leaf, b ; K, node ; nb, bracts ; S, 

 young archegone. C, older leaf with two bracts ; 

 a, antherid ; 6", spermocarp. D, half-mature sper- 

 mocarp (highly magnified). (After Sachs.) 



