2S6 CHARACEM. 



nodal cell rises the peculiarly developed apical cell of the shoot, very large as com- 

 pared 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 Chara ; in Nitella 

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

 termed by Braun ' Wendungszellen.' The large apical cell of the nucule 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 Croivn, consisting in Chara 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 divisions 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 five divisions of the neck of the sac ; and through these clefts the antherozoids 

 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-grains of the envelope become reddish-yellow, the wall 

 of the tubes which lie next the oosphere increase in thickness, become lignified, and 

 assume a black colour; and thus the oosphere, now transformed into an oospore, 

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

 next autumn or spring. 



The Characeae are distinguished by the size of their cells, and by the simple 

 relations of the individual cells to the structure of the whole substance. All the 

 young cells contain nuclei, which at first always lie in the centre of the protoplasm 

 that fills up the whole cell ; each bipartition of a cell is preceded by the absorption 

 of the nucleus and the formation of two new nuclei. As the cells grow vacuoles form 

 in the protoplasm which finally coalesce into a single large vacuole (the sap-cavity). 

 The protoplasm, now clothing the wall as a thick layer, commences its rotatory 

 motion which always follows the longest direction of the cell ; the nucleus about this 

 time becoming absorbed, while grains of chlorophyll are formed. With the growth of 

 the whole cell these grains also grow and multiply by repeated bipartition ; they 

 adhere to the inner side of the outermost thin stationary layer of protoplasm, 

 and take no part in the rotation of the layers which lie further inwards. The 

 rotating protoplasm becomes differentiated, as the cell grows, into portions some 

 very watery and others less watery and denser, the former appearing as hyaline 

 cell-sap in which the latter float in the form of roundish larger or smaller lumps. 

 Since these denser bodies are passively swept along by the rotating clear protoplasm, 

 as may be seen from their tumbling over one another, the appearance is presented 

 as if the cell-sap caused the rotating motion. Together with the denser lumps of 

 protoplasm of less regular form, there are also a number of bodies of globular 

 shape covered with delicate spines, consisting also of protoplasm. The current, as 

 Nageli has shown, is most rapid next the stationary parietal layer, and becomes 



