8 



iSjS. p. 515. He says of //. Opuntia: u This species has not hitherto been recorded as a 

 British zoophyte, but is said to inhabit the Atlantic and Mediterranean. I, however, possess a 

 specimen, formerly belonging to the late Dr. Walker, to which the following note was annexed, 

 in his own handwriting: "Submarine plant from the rocks at Salterness, in Kirkbane. An Bom- 

 bvcina? It covers the rocks with a close turf'. It thus appears to be a native of the shores 

 of the Solway Firth. When a joint was macerated in weak acid, the branched tubes supporting 

 the polypi appeared as they are represented by Ellis, ib. tab. xxv. f. A. 1". 



What ihis plant can have been that "covered the rocks with a close turf', it is difficult 

 to sa\\ It could certainly not have been H. opuntia, which is confined to the tropics. 



Within the tropical zone, in both hemispheres, the genus is well represented and in 

 the Pacific it helps to build up the coral reefs, as is shewn by the presence of Halimcda joints 

 in the borings from the floor of the lagoon at Funafuti. Down to 50 feet below the floor of the 

 lagoon, the joints were sufficiently well preserved to shew the large central filaments on 

 decalcification, and at nearly twice that depth joints of Halimcda were still to be recognised 

 by their form. It is possible that joints of the same species may be found in the sections of 

 the core brought up from still greater depths. 



The geographical distribution of each species will be found below under its own name. 



Methods. The simplest method of preparation for an examination of the peripheral cells 

 of Halimcda in surface view is to clecalcify with Perenyi's fluid and then to tease out with 

 needies. For a side view of the peripheral cells in some species (H. Tttna and H. cuneatd) it is 

 necessary to cut a section of the thallus and this is most easily done with a scalpel before 

 decalcification, the section being afterwards treated on a slide with Perenyi's fluid. 



For an examination of the node it is best to clecalcify and then to place on a slide in 

 a drop of strong Eau de Javelle, till the cell-contents have cleared away. Then stain with 

 methylene blue dissolved in alcohol and afterwards tease or not as may be necessary. The whole 

 operation takes about five minutes when once the preparation has been decalcified. 



I would gratefully acknowledge my indebtedness to Mad me Weber — van Bosse for her 

 most kind invitation to work out the collections of Halimcda, brought home by the "Siboga" 

 and for lending me specimens from the Kützing and Hauck Herbaria : to Professor Askenasy, 

 who has lent me many specimens from his Herbarium and has taken much kind interest in my 

 work : to M. Hartot, who has allowed me to have for examination and study the Decaisne and 

 Bory types in the Paris Museum and has given me much kind encouragement ; to M. Beccaki 

 for lending me a type specimen of Zanardini : to Professor Nordstedt for taking much trouble 

 in procuring me good photographs of plants, of which he was unable to send me the originals : 

 to Dr. Perceval Wright for lending me some of the Harvey specimens from Trinity College, 

 I )ublin : and to Professor Engler for allowing me to have a type specimen from the Berlin 

 Museum for examination. I also here gratefully record the kindness shewn me by the late 

 Professor J. G. Agardh, in lending me the type of Halimcda cordata. He wrote to me that 

 at his advanced age it was an effort to him to part with a valuable type specimen even for 

 a few days; but he was kind enough to make the sacrifice and the letter he wrote acknow- 

 ledging its return was foliowed a few days later by the news of his death. To Mr. V. H. Blackmax 



