176 



MORPHOLOG Y. 



ft" 



Class Charophycese, Order Charales. 



386. The Charales are by some thought to represent a distinct class of 

 algae standing near the mosses, perhaps, because of the biciliate character of 

 the spermatozoids. There is one family, the Characeae. The plants occur 

 in fresh and brackish water. Aside from the peculiarity of the reproductive 

 organs they are remarkable for the large size of the cells of the internodes 

 and of the "leaves," and the protoplasm exhibits to a remarkable degree 



the phenomenon of "cyclosis" 

 (see paragraphs 17-20). Three 

 of the genera are found in North 

 America (Chara, Nitella (Fig. 8) 

 and Tolypella). 



386a. The complicated struc- 

 ture of the sexual organs shows a 

 higher state of organization than 

 any of the other living algas 

 known. While the internodes in 

 Nitella are composed of a single, 

 stout cell, some times a foot or 

 more in length, the nodes in all are 

 composed of a group of smaller 

 cells. From the lateral cells of 

 this group lateral axes (sometimes 



F{ z- ^ 2a - called leaves) arise in whorls. 

 Reproductive organs of Chara fragilis. A, , ~,. .. , . . 



a central portion of a leaf, b, with an anther- In Nitella the internodes are 



idium, a, and a carpogonium, 5, surrounded n .,Vfrl Knf- in mnct cr>/~ipc r>f 



by the spirally twisted enveloping cells; c, naked > but ln most species ot 



crown of five cells at apex; /9, sterile lateral Chara they are corticated, i.e., they 

 leaflets; /?', large lateral leaflet near the fruit; , , , .. 



0", bracteoles springing from the basal node are covered by a layer of numer- 



sk; w, nodal cell of leaf; u, intermediate downward from the nodes at the 



cell between w and the basal-node cell of . , , . . . . , 



the antheridium; /, cavity of the internode base of the whorl of lateral shoots. 



386b - The se - 



. 



situated at the nodes of the 

 whorled lateral shoots, and consist of antheridia and carpogonia. Most of 

 the plants are monoecious, and both antheridia and carpogonia are often 

 attached to the same node, the antheridium projecting downward while the 

 carpogonium is more or less ascending. The sexual organs are visible 

 to the unaided eye. The antheridium is a globose red body of an exceed- 

 ingly complicated structure. The sperms are borne in several very long 

 coiled slender threads which are divided transversely into numerous cells. 

 The carpogonium is oval or elliptical in outline, the wall of which is com- 

 posed of several closely coiled spiral threads enclosing the large egg. 



