192 
Batters. — On Schmitziella 
stated, the marginal row of filaments, usually composed of 
short two-celled threads, always remains sterile, forming a ring 
around the empty sorus 1 . 
The development of the sorus proceeds from the centre out- 
wards : first the central group of paraphyses is formed ; then 
the sporangia surrounding it come to maturity and are dis- 
charged through the opening in the cell-wall of the Cladophora 
made for that purpose by the central paraphyses ; then follows 
the maturing and discharge of the sporangia further removed 
from the centre, those nearest the edge of the sorus being the 
last to mature ; finally only the narrow ring of sterile marginal 
filaments, the central group of paraphyses, and here and there 
an isolated paraphysis, remain. 
The cystocarpic sori in the same manner as the tetrasporic 
are scattered over the surface of the thallus. The same almost 
simultaneous upward growth of the basal cells takes place, 
forming a compact sorus, the central threads of which are 
composed of from three to five cells, while those of the re- 
mainder of the sorus are much shorter. Only these central 
threads develope into carpogenic filaments, a very few of them 
continuing sterile and forming paraphyses, similar to those of 
the central group in the tetrasporic sori. While the apical cells 
of the sterile filaments remain comparatively short, those of 
the central group of filaments lengthen and form the carpo- 
gones, elongating upwards into long thin trichogynes, which, 
like the central group of paraphyses in the tetrasporic sori, 
locally raise and finally break through the outer layer of the 
cell-membrane of the Cladophora in united bundles which pro- 
ject for some distance through the opening thus made (Fig. 12). 
The cell-membrane of the Cladophora is rather tough, and 
although the sharp-pointed paraphyses usually pierce it with- 
out bending or distortion of any kind, the trichogynes are 
frequently bent when they come in contact with its under 
1 The marginal ring of short paraphyses represents in a rudimentary form 
the enclosing wall of the conceptacles in which the reproductive organs of the 
other members of the Corallinaceae are developed. In Schmitziella , therefore, 
the transition from the unenclosed sorus to the conceptacle is well-marked. 
