Phylum Phaeophyta [ 89 



gametes are flagellum-bearing cells of the type usual in brown algae. The eggs are 

 capable of germination without fertilization, reproducing the haploid stage. Diploid 

 individuals bear clusters of unilocular sporangia. 



It is only in the life cycle that the Cutlerialea are decidedly different from higher 

 Sporochnoidea such as Desmarestia. Their evolutionary origin is explicable by the 

 hypothesis of a single mutation which enabled the haploid stage to exhibit the com- 

 paratively complicated morphology of the diploid stage, instead of being rudimentary 

 as in all Sporochnoidea except Ralfsia (and the exceptional life cycle of Ralfsia 

 would be explained by a similar mutation in some primitive example of Sporochnoi- 

 dea, such as Myrionema) . 



Older 6. Laminariea [Laminarieae] Greville Alg. Brit. 24 (1830). 



Order Pycnospermeae Kiitzing Phyc. Gen. 333 (1843). 



Order Laminariaceae Haeckel Gen. Morph. 2: xxxv (1866). 



Laminariales Oltmanns Morph. u. Biol. Alg. ed. 2, 2: 2 (1922). 



Order Laminariales Engler and Gilg Syllab. ed. 9 u. 10: 27 ( 1924). 



Order Dictyosiphonales Setchell and Gardner in Univ. California Publ. Bot. 

 8: 586 (1925). 



Order Punctariales Kylin in Kungl. Fysiog, Sallsk. Hand!, n. f. 44, no. 7 : 93 

 (1933). 

 Brown algae with motile spores, the haploid stages reduced to microscopic dimen- 

 sions, the diploid stages thallose, growing in intercalary fashion. 



This numerous group, like the preceding small one, is evidently a specialized off- 

 shoot from order Sporochnoidea. The familiar examples are the kelps, whose large 

 diploid bodies are differentiated into definite members. Kylin considered his order 

 Punctariales to represent the transition to the kelps. They are thallose, without dif- 

 ferentiation of members, but their microscopic and reproductive characters, as ob- 

 served in Soranthera by Angst (1926, 1927), tend to confirm Kylin's opinion, and 

 they are accordingly included in the same order with the kelps. Papenfuss (1947) 

 pointed it out that the Punctariales of Kylin are essentially the same group as the 

 Dictyosiphonales of Setchell and Gardner. 



Sauvageau (1915) first showed that the reproduction of kelps is sexual. The 

 grossly visible individuals produce zoospores; these, on germination, produce micro- 

 scopic filamentous haploid individuals, generally of distinct sexes, releasing gametes 

 from unicellular gametangia. The eggs are without flagella, and it is characteristic 

 of them that in emerging from the oogonia they become attached at the opening 

 (Kylin, 1916, 1933; Myers, 1928; McKay, 1933; Kanda, 1936; Hollenberg, 1939). 

 The same things are true in Soranthera, except that the eggs, although much larger 

 than the sperms, are also flagellate. 



The visible bodies of kelps consist of three kinds of members, holdfasts (hapteres), 

 being stout root-like growths by which the individuals are anchored to rocks, and 

 stalks and blades comparable to stems and leaves. Growth is most active at the sum- 

 mits of the stalks. The histology is the same in all members (A. I. Smith, 1939). 

 There is a superficial photosynthetic tissue of small cells rich in plastids; on the hold- 

 fasts and stalks, this tissue is meristematic, adding cells to the tissue within and in- 

 creasing the thickness. Internally there is a cortex of larger cells with fewer plastids. 

 In the center there is a medulla containing trumpet fibers, filaments whose cells are 

 expanded where they meet and marked by pit-pairs. In the trumpet fibers of Nereo- 

 cystis there are actual perforations from cell to cell. The trumpet fibers are not quite 



