168 THALLOPHYTA. [CH. 



from Acetahularia. The genus Acicularia formerly restricted 

 to fossil species is now applied also to this single living species 

 Acicularia SchencM. 



The genus is thus defined by Solms-Laubach : — 



" Discus fertilis terminalis e radiis inter se conjunctis formatus, coronis 

 et inferiore et superiore praeditis, sporae massa mucosa calce incrustata 

 coalitae, pro radio spiculam solidam cuneatam formantes^." 



As Solms-Laubach points out in his recent monograph, 

 Munier-Chalmas' conjecture, "which had little to support it 

 in the fossil material, has been more recently proved true in 

 the most brilliant fashion by the discovery of a living species 

 of this genus." 



1. Acicularia Andrussowi Solms^. Fig. 33, C and D. This 

 species was first described by Andrussow' as Acetahularia 

 miocenica from the Crimea. It occurs in Miocene rocks south 

 of Sevastopol, and, with Ostrea and Pecten, forms masses of 

 white limestone. 



In each sporangial ray of the disc the cavity contains a 

 calcareous spicula bearing spore cavities in four rows. " Round 

 each spore-cavity there is a circular zone which stands out, 

 when viewed in reflected light, through its white colour against 

 the central mass of the spicule, though a sharp contour is not 

 visible*." Fig. 33, C, is taken from a somewhat diagrammatic 

 sketch by Andrussow; it shows ten of the fertile rays of 

 the disc. The thick walls of the chambers are seen in the two 

 lowest rays, and in the next two rays the spore-cavities are 

 represented. A more accurate drawing, from Solms-Laubach's 

 memoir, is reproduced in fig. 33, D. The calcareous spicule 

 with numerous spore-cavities shown in fig. 33, H, is from a 

 fertile ray of the recent species Acicularia Schencki. This 

 corresponds to the spore-containing calcareous matrix in each 

 ray of the disc of Acicularia Andrussowi Solms. The spicule 

 copied in fig. 33, F from one of Carpenter's drawings' of an 



' Solms-Laubach loc. r.it. p. 32. 2 xMd. p. 34, PI. iii. fig. 13. 



3 Andrussow (87). ' Solms-Laubach {95") p. 11. 



= Carpenter (62) PI. xi. fig. 82. 



