CARPOSPOREM. 



299 



whip-shaped filaments, which, being coiled round and round, fill up the interior of the 

 globule (Fig. 198, B). Each of these filaments (the number of which amounts to about 

 200) consists of a row of small disc-shaped cells (Fig. 198, D, E, F), numbering from 

 100 to 200. In each of these 20,000 to 40,000 cells is formed an antherozoid, a slender 

 spiral thread, thickened behind, and bearing at its pointed end two long fine cilia 

 (Fig. 198, G). When perfectly ripe, the eight shields fall apart, their spherical 

 curvature becoming diminished; the antherozoids leave their mother-cells and move 

 about in the water. This breaking up appears generally to happen in the morning, 

 and the antherozoids are in motion for some hours, till evening. 



The mature Carpogonium (Nucule), when ready for fertilisation, is a longer or 

 shorter prolate spheroid ; it is placed upon a short pedicel, visible externally only in 

 Nitella, and consists of an axial row of cells, closely surrounded by five tubular cells 

 which are coiled round it spirally. The whole must be considered as a metamorphosed 

 branch. The lowest cell corresponds to the lower internode of a branch ; it bears a 

 short central nodal cell, around which the five enveloping tubes spring like a whorl of 

 leaves. Above the nodal cell rises the peculiarly developed apical cell of the branch, very 

 large as compared to the other parts, and ovoid. At its base, immediately above the 

 nodal cell, an inconspicuous hyaline cell is separated at an early stage in Cbara; in Nitella 

 a somewhat disc-shaped group of similar cells takes its place, which have been termed 

 by Braun ' Wendungszellen,' and which I consider as forming a very rudimentary 

 trichophore. The large apical cell of the carpogonium is filled with a number of 

 drops of oil and grains of starch as well as with protoplasm ; it contains pure hyaline 

 protoplasm only in its apical region (the apical papilla). The enveloping tubes, which 

 contain a quantity of chlorophyll, project above the apical papilla and bear the Cronvn, 

 consisting in Cbara of five larger, in Nitella of five pairs of smaller cells, which have 

 already been separated at an early stage from the enveloping tubes by septa. Above the 

 apical papilla and beneath the crown, which forms a compact lid, the five enveloping 

 tubes form the neck which encloses a narrow cavity, the apical cavity; above the 

 papilla this cavity is of an obconical figure narrowing upwards, the five segments 

 of the neck projecting and forming a kind of diaphragm, through the central very 

 narrow opening of which the union with the upper roomy part of the apical cavity 

 is effected. This is closed above by the crown ; but, at the time of fertilisation, it opens 

 externally by five clefts between the coronal cells ; and through these clefts the anther- 

 ozoids penetrate into the apical space filled with hyaline mucilage, to find their way into 

 the apical papilla of the oosphere, where the cell-wall is apparently absent. After 

 fertilisation the chlorophyll-granules of the envelope become reddish-yellow, the wall of 

 the tubes which lie next the oosphere increases in thickness, becomes lignified, and 

 assumes a black colour ; and thus the oosphere, now transformed into a carpospore, 

 becomes surrounded by a hard black shell with which it falls off, to germinate in the 

 next autumn or spring. 



With regard to the various processes of development, I will here describe only those 

 of the antheridia and carpogonia. 



Antheridia. The order of development of the cells has already been exhaustively 

 described by A. Braun in the case of 'Nitella syncarpa and Chara Baueri ; it agrees with 

 that of Nitella Jlexilis and Chara fragilis. In Nitella the terminal cell of the leaf becomes 

 the antheridium ; the oldest leaf of a whorl first forms its antheridium, the others follow 

 according to their age ; the antheridia are recognisable even in the earliest state of 

 the whorl of leaves. In Fig. 200, A, is shown a longitudinal section through the apex 

 of a branch, t being its apical cell ; its last-formed segment has already been divided 

 by a septum into a nodal mother-cell AT and an internodal cell lying beneath it; beneath 

 this lies the node with the last whorl of leaves ; h is its youngest leaf, bK the basal node 

 of the oldest leaf which already consists of the segments 7, //, 77/ ; a is the terminal cell 

 of this leaf which is becoming transformed into the antheridium. While the antheridium 

 is becoming developed, the leaf also undergoes still further changes which must be first 



