132 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



Harvey (1849, p. 2), De Bary (1872, p. 238), and Sachs (1875, p. 278) were 

 the first to consider the Charophyceae as forming a group removed from both the 

 thallophytes and the bryophytes. They were followed by Migiila (1890-1897), 

 who erected the phylum Charophyta. Migula thought that both the Bryophyta 

 and Charophyta probably had evolved from green algae but had developed 

 along different lines. Many botanists, including a large number of students of 

 the Charophyceae, agree with Migula in regarding the assemblage as constituting 

 a distinct phylum, although it is not always clear from their writings whether 

 they consider this phylum as belonging with the algae (thallophytes) or not. 

 Groves and Bullock-Webster (1920, p. 1) remark: "The Charophyta are a small 

 group of Cryptogams, and occupy a peculiarly isolated position, having no clear 

 affinity with any other plants." Oltmanns (1922a, p. 457) sa^'s that he at times 

 was doubtful whether he should include the group in his book on the algae. 



Fritsch (1935, pp. 447, 465-466) although admitting (p. 447) that "the sex 

 organs, and in particular the antheridium, though quite unparalleled among the 

 algae, are equally unique when considered in relation to other groups of plants," 

 nevertheless places the group as an order in the Chlorophyceae. Smith, who 

 omitted them from the first edition (1933) of his Fresh-ivater Algae of the 

 United States later (1938, 1950) considered them as constituting a separate 

 class among the green algae. 



Although the Charophyceae differ from green algae in a number of features, 

 the most important single character which removes them from this group or, 

 for that matter, perhaps from all thallophytes lies in the structure of the anthe- 

 ridium. As a primary and integral part of its development, this organ cuts off 

 an outer series of sterile cells, the shield cells, which function as a protective 

 layer to the later produced inner fertile cells. Since the exposed nature of the 

 reproductive organs remains as one of the few clear-cut characters whereby thal- 

 lophytes may be separated from plants of a higher evolutionary level, it may 

 thus even be questioned, as have Migula, Oltmanns, and many others, whether 

 the Charophyceae should be classified as algae. 



In this connection it is of interest to consider Goebel's (1930) ingenious 

 interpretation of the antheridium. He regards it as a compound structure con- 

 sisting of eight congenitally fused short branches, each composed of three cells 

 — an apical cell (corresponding to a shield cell) and a segment cell which has 

 divided into two cells, the basal of which has become a capitulum cell and the 

 other a manubrium cell. 



On this interpretation of Goebel each cell of the spermatogenous filaments 

 of the compound antheridium is an antheridium, as in many algae. It should 

 be remembered, however, that in many plants above the level of thallophytes 

 (e.g., bryophytes) the sperms are also produced in individual cells and yet 

 the antheridia are not considered compound structures. It may be emphasized, 

 furthermore, that the method of initiation of the eight short branches through 

 longitudinal division of an initial cell does not conform to the usual method 

 of branch initiation in the Charophyceae. But even if Goebel's interpretation 

 should be correct, the fact remains that a reproductive structure is formed in' 

 which the fertile cells are protected by a primarily produced sterile covering. 

 Fritsch retains the Charophyceae in the Chlorophyceae largely because they 

 have green plastids, produce starch, are haploid, and the Nitelleae have a simple 



