ECOLOGY AND TAXONOMY OF Holimeda 43 



of the changes associated with yet older segments are also included in 

 the account if they can be used in species identification. 



(b) Preparation of mMer'ial 



(i) For nodal structure. Generally all the required information can 

 be obtained by removing from the nodal region a thin rectangular strip 

 approximately 6 mm long, 1-5 mm broad and the thickness of the 

 segments included. The long axis of the rectangular strip should be 

 along an imaginary line connecting nodes of sequential segments. The 

 sample should include a small portion of the segments adjoining the 

 node. If material is scarce, as it generally is with herbarium specimens, 

 one can generally manage with only part of a node. By such 

 parsimonious tactics, adjoining segments remain attached and the 

 continuity of the thallus is maintained. If material is ample, as generous 

 a strip can be cut as is desired. This rectangular strip may be sectioned 

 or dissected. 



For routine taxonomic examination the information on nodal 

 structure often can be obtained from sections, and I prefer this 

 approach because one frequently can obtain data on other microscopic 

 characteristics from the same preparation. 



A satisfactory technique is to section the strip lengthwise on a 

 smooth card with a razor blade, using the short edge of a microscope 

 slide as a guiding edge. 



With a slightly moistened needle transfer the sections to a drop of 

 water on a slide, decalcify with about 20% hydrochloric acid, remove 

 excess acid with a tissue, and resuspend the sections in water. This 

 sometimes is sufficient preparation, particularly if the material is 

 living, and all that is needed before examining with a compound 

 microscope is to add a coverslip. The slides subsequently may be made 

 semi-permanent by infiltrating with glycerine or another medium 

 if desired. 



With some types of nodal structure, and with dried thin specimens, 

 some teasing or dissecting apart of deflated filaments in the sections, 

 with fine needles or fine pins such as insect mounting pins, is required 

 before examining. 



Entire nodes also may be decalcified and dissected for the required 

 information. This technique is the obvious one for a species such as 

 cryptica with only one nodal filament. For some species, however, the 

 resultant numbers of filaments make elucidating the structure more 

 difficult than working from sections. 



(ii) For surface of peripheral utricles. The diameters of the 

 peripheral (primary) utricles and siu-face detail are obtained from a 



