130 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



have passed through a period of hibernation. Adventitious long branches may develop 

 from the nodes of hibernating plants or parts that have become detached. Frequently, 

 tuberlike organs of vegetative propagation are formed on the rhizoids or at the nodes of 

 buried parts of the long branches. 



Sexual reproduction is oogamous. The plants may be monoecious or dioecious. The 

 oogonia and antheridia are produced at the nodes of the primary laterals of limited 

 growth. 



The antheridia are much more complex than those of other thallophytes. The anther- 

 idial initial divides by two intersecting longitudinal and a median transverse wall. Each 

 of the octants so formed then divides by two periclinal walls. The eight peripheral cells, 

 known as the shield cells, constitute the antheridial wall, the middle series of cells form 

 what is known as the manubrium, and the innermost eight cells constitute the primary 

 capitulum. Through the elongation of the manubrium cells and the enlargement of the 

 capitulum cells the manubria become laterally separated from one another in the mature 

 condition. The shield cells and the manubrium cells do not undergo division during the 

 further development of the antheridium. Through division each primary capitulum pro- 

 duces six secondary capitulum cells which may or may not produce tertiary and quater- 

 nary capitula. The secondary capitula, but at times also those of lower and higher order, 

 cut off initials which give rise to branched or unbranched septate spermatogenous fila- 

 ments, each cell of which eventually forms a single, elongated, anteriorly biflagellate 

 sperm. 



The oogonia are like those of thallophytes in being single-celled and at first naked 

 structures. During their development the cell below the oogonium produces five corti- 

 cating filaments that invest the oogonium. These filaments remain undivided except at 

 their apices, where each cuts off by transverse division one or two coronal cells. The 

 single living family (Characeae) is divided into two subfamilies on the basis of the 

 formation of one (Charoideae) or two (Nitelloideae) tiers of coronal cells. Only one 

 egg is formed in each oogonium. In the mature condition the cortical filaments are 

 spirally twisted (clockwise in all living species, counterclockwise in some fossil forms) 

 about the oogonium. 



Meiosis occurs during germination of the zygospore. At first there is produced a 

 protonema, from the primary branch of which the mature plant arises as a lateral branch. 



The living Characeae are essentially freshwater in occurrence. Many of the fossil 

 forms were marine in distribution (Peck, 1934, p. 101). 



History: The first published record of the designation Chara in its present 

 sense apparently is that by the herbalist Daleehamps (1587, p. 1070) who gave 

 it as the popular name of an Equisetum-like aquatic plant used by the inhabi- 

 tants of Lyons to scour plates and other utensils. Vaillant in 1721 formally 

 erected the genus Chara. During the following one hundred and fifty years these 

 plants had an extremely checkered systematic history. Many of the early botan- 

 ists regarded them as species of Equisetum or Hipimris. Linnaeus (1753) con- 

 sidered Chara a genus of algae. Adanson (1763, p. 472) placed it in family 56, 

 Ara (aroids) of the flowering plants. Others, as for example De Candolle (1805, 

 p. 584), associated the genus with the Naiadaceae. 



In 1815 Richard {in Bonpland and Humboldt) proposed (as a nonien nu- 

 dum) the family Characeae and regarded it as belonging to the angiosperms. 

 Many early botanists, however, such as C. Agardh (1824), who established the 

 genus Nitella, Wallroth (1833), Endlicher (1836), Kiitzing (1843, 1849), and 

 others, had no hesitation in according these plants a place among the algae. On 

 account of the spirally arranged ensheathing filaments of the oogonium, Wallroth 

 (1833) erected for them (and a number of unrelated genera) the order Gyrophy- 

 kea (one of four which he recognized in the algae), and this name was later used 

 for the group by Rabenhorst (1847). 



