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POSITION OF THE DICTYOTACE^I. 



469 





further and seeking to ascertain their position in the Phceophycece. 

 In this connection I attach very great importance to the obser- 

 vations of Eeinke on the Tilopteridea * The members of this 

 group have a thallus which is Sph a celari a Aike below, Ectocarpus- 

 hke above. They have large non-motile quadrinucleate spores 

 (potential tetraspores) borne by wholly asexual plants (e. g. Haplo- 



lik 



) 







*^ / J — — — /J **" **V/V UAlii \J\J £L \S t-1 114'* JJVU U1VI/IAV \S\SKt ** **• V* v*^ 



e those of the Dictyotacece, external fertilization, plurilocnlar 

 antheridia, antherozoids like those of the Cutleriaceas and the 

 Jfucacea. The seedlings resulting from the germination of the 

 asexual spores are, as Eeinke states, very much like the corre- 

 sponding seedlings of the Dictyotacex as described by him in 1878, 

 and the description he gives of the formation of proliferations 

 'rom the root- hairs in Tilopteris globosa would apply, almost word 

 tor word, to the case of Bictyopteris polypodioides. Except in 

 the absence of apical growth, the Tilopteridete form an easy transi- 

 tion to the Dictyotace<e. Bornetf has this year described the 

 species Pylaiella fulvescens, Thur., showing that its intercalary 

 unilocular sporangia contain, each, a single large zoospore which 

 18 ln size and all essential points, except its apparent power of 

 ready germination, like the zoosphere of the Cutler iacece . This 

 plant with these organs and its creeping thallus were known 

 to Thuret and Bornet in 1870. Bornet has not yet been able 

 to find antheridia. In the possession of these zoosphere-like 

 bodies Pylaiella fulvescens agrees with Pylaiella nana, Kjellm., 

 and apparently Pylaiella littoralis. 



Thuret and Bornet, in 1876, described J in Ectocarpus Zebelii, 

 Kuetz.,and Ectocarpus secundus, Crouan, two kinds of plurilocular 

 sporangia. I n the one kind they found ciliated bodies of small 

 jke, indistinguishable from the antherozoids of Cutler ia or Fucus. 

 *n the other kind bodies like the zoospheres of Cutleria, like the 

 zoospores of Pylaiella fulvescens are found, but whether they can 

 germinate directly or need first fertilization is still a question of 

 observation. The condition of the reproductive organs in Ectocar- 

 P us pusillus, Ectocarpus siliculosus, Qiraudia sphacelarioides, and 

 Scytosiphon, as ascertained by Goebel and Berthold, is well known 

 from the English translation of Goebel's ' Outlines of Classification 



* Reinke, in Bot Zeit. t. ii. & iii. nos. 7-9 (1889). 

 Bornet, " Note sur Y Ectocarpus (Pylaiella) fulm 



u ^. de Bot. i; (1889), no. 1, pi. i. 

 X Thuret and Bornet, * fitudes Physiologiques,' p. 24. 



ens, Thuret," in Re 











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