170 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



groups was later elevated to the rank of order (with altered circumscription, 

 of course). 



Between 1848 and 1917, these algae were divided by different authors into 

 two, three, or four major taxa. Thuret (1855, pp. 5-15) recognized four groups: 

 Phaeosporeae, Tilopterideae, Dictyoteae, and Fucaceae. Hauck (1883) recog- 

 nized three orders: Fucoideae (with one family), Dictyotaceae (with one family), 

 and Phaeozoosporeae (with ten families). Hauck 's three groups were retained 

 by De Toni (1895) except that he used, respectively, the names of Cyclosporinae 

 (a designation proposed by Areschoug, 1847, for the Fucaceae), Tetrasporinae, 

 and Phaeozoosporinae. 



Kjellman (1891-1893) divided the Phaecophyceae into the two groups Phaeo- 

 sporeae and Cyclosporeae (with the single family Fucaceae) and removed the 

 Dictyotaceae to an independent group Dictyotales, which he considered as so 

 different from other brown algae that they could not be properly placed with 

 them (see also Falkenberg, 1882, pp. 169, 230-234). (Because they commonly 

 form four immobile spores in their unilocular sporangia, which thus resemble 

 the tetrasporangia of red algae, the Dictyotales were a stumbling block to many 

 students of the algae of the last century.) The Phaeosporeae were divided by 

 Kjellman into the two subgroups Zoogonicae and Acinetae (which included only 

 the Tilopteridaceae). It is apparent that as far as the major categories are con- 

 cerned Kjellman's system differed but little from that of Thuret. 



Oltmanns (1904) segregated the Phaeophyceae into the three groups Phaeo- 

 sporeae, Akinetosporeae (a designation proposed by Bornet, 1891, p. 370), and 

 Cyclosporeae. The Akinetosporeae received only the Tilopteridaceae (character- 

 ized by their immobile monosporangia), but in contrast to earlier systems, Olt- 

 manns placed the oogamous Dictyotaceae as a second family with the likewise 

 oogamous Cyclosporeae (Fucaceae). 



In 1917 Kylin revised the classification of the Phaeophyceae, basing his sys- 

 tem largely on developmental and nuclear cycles. He recognized five orders: 

 Phaeosporeae, Tilopteridales, Dictyotales, Laminariales, and Fucales. The es- 

 sentially new feature here is the establishment of the order Laminariales for 

 those Phaeosporeae of earlier systems that had been found to possess an alter- 

 nation of heteromorphic generations. 



During the next ten years the old order Phaeosporeae was further subdi- 

 vided into the following seven orders: (1) Ectocarpales (Setcliell and Gardner, 

 1922, Oltmanns, 1922b; see Papenfuss, 1947, p. 398, fn., regarding the dates of 

 the works by Setchell and Gardner, and Oltmanns); (2) Sphacelariales (Olt- 

 manns, 1922b); (3) Cutleriales (Oltmanns, 1922b); (4) Chordariales (Setchell 

 and Gardner, 1925); (5) Sporochnales (Sauvageau, 1926); (6) Desmarestiales 

 (Setchell and Gardner, 1925); (7) Dictyosiphonales (Setchell and Gardner, 

 1925). 



Utilizing the recently acquired knowledge of the structure and reproduc- 

 tion of the Phaeophycophyta, Kylin in 1933 erected a new system of classifica- 

 tion of these algae. He divided them into three classes and a total of twelve 

 orders, one of which (the Punctariales) he established in this paper as a segre- 

 gate from the Ectocarpales. The first class, the Isogeneratae, received forms that 

 showed an alternation of isomorphic generations. It included the orders Ecto- 

 carpales, Sphacelariales, Cutleriales, Tilopteridales, and Dictyotales. The second 



