INTRODUCTION TO CRYPTOGAMIC BOTANY. 161 



frond, as in Halhneda, have a tuft of filaments, which, like 

 those of Acetabularia, are decidedly articulate, and indicate, 

 therefore, a different alliance ; these do not, apparently, bear 

 any fruit. Other calcareous species have been described, re- 

 sembling in structure Codium and Gaulerpa, or approximating 

 higher groups, but they do not throw much light upon the 

 nature of the fruit, and examination in their native locality 

 would, probably, show that all are not intimately related. 

 Dasycladus has been illustrated in Derbes and Solier's me- 

 moirs, and is also figured by Kiitzing, and seems rather a 

 compound Conferva than Vaucheria. In the genus Flabel- 

 laria, globose cysts are produced here and there upon the 

 component threads, near the edges of the fan-like expan- 

 sions, and it is probable that the contents of these are re- 

 solved into zoospores, in the same manner as in so many 

 other Algge. 



134. Finally, the numerous species of Caulerpa and its sub- 

 genera deserve notice, from the beauty of their form, and the 

 singularity of their structure. They are strictly unicellular, 

 however varied the external appearance assumed by the plants 

 may be. The most singular point about them is, that from 

 their walls complicated branches are sent out into the mass 

 of green granules, which fills the frond, ramifying in every 

 direction, and affording, doubtless, great support against 

 disturbing external agents. The chemical character of these 

 threads requires to be studied. They are, in fact, extremely 

 anomalous productions, and it appears that Decaisne is 

 quite right in his views, as to their origin. The cell-walls 

 from which they arise are very thick, and in some instances 

 cartilaginous, and Decaisne* has figured concentric rings in 

 their lining substance, indicative of successive growth. He 

 jemarks, moreover, that this is not the only case in which the 

 matter, with which the threads in the inside of the frond 

 are bathed, contains granules. The threads in some of the 

 cases which he mentions, as Splachnidium, Champia, &c., 

 are of course of a very different nature from the processes just 



* Decaisne, Plantes de I'Arabie Heureuse, tab. 6, B. 5. Nag. Zeits. 

 vol. i. tab. 3. 

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