4 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



SporoMthon ptychoides, which Foslie 1 and Lemoine 2 consider to be 

 synonymous with A. erythraeum. The sori or the emptied sporangial 

 cavities appear also to be much less regularly embedded or overgrown 

 by new tissue than is the case in A. erythraeum, if one may judge 

 from Rothpletz's original description, 3 Heydrich's figure 3, 4 Le- 

 moine's figure 29, 2 and the descriptions given by the last-named writ- 

 ers; however, Foslie 5 remarks of A. erythraeum that "the sori are 

 partly to be found overgrown in great numbers by new formed tissue, 

 partly, however, they are not to be seen in section." In A. episporum, 

 the sporangia themselves have never been seen except close to the 

 surface ; the emptied sporangial cavities do not show in a rough frac- 

 ture or in an ordinary ground section, but irregular traces of them 

 are often to be found in thin microtome sections of decalcified ma- 

 terial. The sori of A. episporum are so superficial that their cover- 

 ing, after the discharge of the spores, appears to die and is flaked off 

 together with more or less of the intersporangial parts, and the new 

 tissue growing up from the base of the sorus shows only occasionally 

 and imperfectly the outline of the former sporangial cavities. 



Kothpletz's original description of his Lithothamnium erythraeum 

 leaves one in some doubt as to whether he found the contents of the 

 sporangium divided or undivided ; he uses the term " Tetrasporen," 

 but the measurements that he gives for these " Tetrasporen " are 

 such as commonly belong to the whole sporangium in this group. 

 In Heydrich's first description ,J of his SporoMthon ptychoides, the 

 " Tetrasporangien " are said to be " meist ungetheilt, selten zwei- 

 theilig," but a little later 7 he figures four tetraspores in a sporangium, 

 arranged in the " cruciate " manner. But this mode of division being 

 at variance with the prevailing ideas as to the arrangement of the 

 spores in the Coral linacese, Foslie, 8 a little later in writing a diag- 

 nosis of the genus ArchaeoMthothamnium inserted a question mark 

 after "sporangia * * * imparted or cruciate?" and this sign of 

 doubt as to the cruciate division has been repeated by later writers. 9 

 In A. episporwm the mature sporangia are commonly and normally 

 4-parted in an irregularly " cruciate " fashion, but often the division 

 axes of the two pairs of spores are at right angles to each other, so 

 that only three spores are- visible in a lateral view, and occasionally 



1 giboya Exped. Monog., No. 61, p. 38. 1904. 



2 Ann. Inst. Oc<5anog., vol. 2, pt. 2, p. 67. 1911. 



3 Rothpletz, A. Bot. Centralb., vol. 54, p. 5. 1893. 

 * Ber. Deuts. Bot. Ges., vol. 15, p. 68. 1897. 



5 Siboga Exped. Monog., No. 61, p. 41. 1904. 

 °Ber. Deuts. Bot. Ges.. vol. 15. p. 69. 1897. 

 7 Idem, pi. 18, fig. 3. 



s Kgl. Norske Vidensk. Selsk. Skr. 1900, pt. 5, p. 8. 1900. 



9 De Toni, Syll. Alg., vol. 4, p. 1721, 1905; Svedelius, in Eng. & Prantl, Nat. Pflanzen- 

 fam., vol. 1, pt. 2 ; Nachtsage, p. 267. 1911. 



