39 



f. typica. Supra-dichotomial constrictions more long-necked than in f. typica (compare figs. io6« 

 and 109^). (NB. The plant figured — fig. 108 — is not a dried plant, but a spirit specimen). 



Udotea lacerata was founded by Harvey on specimens collected by him in the Friendly 

 Islands and issued without description in his Alg. Exsicc. Friendly Islands under n° 86 (fig. 105). 

 The first diagnosis was published in Till Alg. Syst. V. (1887) p. 54 by J. G. Agardh, who 

 rightly places the species in Avrainvillca. He points out a similarity in habit to Udotea 

 Desfontainii and discusses the possibility of its identity with Udotea sordida Mont. (Philippines, 

 Cuming) a point which, for want of material of the latter plant, he was unable to decide. He 

 also debates its possible affinities. 



The typical form of A. lacerata is a well-marked plant, varying but slightly in habit. 

 It is characterised by the production of many small, thin fronds borne on slender stalks arising 

 from a repeatedly branched stem. The Siboga specimen (fig. 107) agrees nearly with the 

 type (fig. 105). It is constant also in the characters of the frond-filaments (fig. 106) which 

 are similar to those of A. sordida, both in size and form. They are also in size much like 

 the filaments of A. amadelplia, being about 25 [j. wide, and cylindrical not torulose in the 

 older parts of the filament, while towards the apices they diminish to 6 u. in width and often 

 become irregularly subtorulose for a short distance below the apices. The apices are not how- 

 ever unilaterally torulose and tortuous as in A. amadelplia; nor do they, as in that species, 

 intertwine so as to form a pseudo-cortex. Even in reef-forms A. lacerata is a much more 

 slender plant than A. amadclpha-, and in deep water A. lacerata differs but little from its 

 reef- form, whereas A. ai/iadelpka in deep water grows to three times the size of its reef- form. 

 A. lacerata differs from A. pacifica in structure, the filaments of the latter being very torulose 

 and not cylindrical. 



From A. sordida, A. lacerata differs in habit and in geographical distribution. A. sordida 

 has a stem which is either simple or once dichotomous, thus bearing one or rarely two rounded 

 fronds with cordate base, whereas in A. lacerata the stem is usually divided into several slender 

 long or short branches, each bearing a frond which is small, membranaceous and fimbriate : also 

 A. sordida is limited to the West Indies where it is a well-known plant. In the characters of 

 the frond-filaments alone it is difficult to find a satisfactory distinguishing feature between the 

 two species. 



var. robustior. 



In the British Museum are several specimens collected by Mr. H. N. Ridlev at Singapore 

 (fig. 108 is a spirit-specimen), which correspond exactly with A. lacerata in structure, though 

 diverging in habit. They are stouter and browner, and have larger and shorter-stalked fronds 

 which are more crowded and more overlapping than in the typical A. lacerata. We do not 

 know whether they came from deep water or shallow. In habit they approach the surf-form 

 of A. amadelplia, but differ in structure, the tapering apices of the frond-filaments being less 

 tortuous, enodulose, not hooked and felted together into a pseudo-cortical layer as in A. 

 amadelplia. Var. robustior occurs in the western limits of the distribution-area of A. lacerata and 

 well outside the area of A. amadelplia. 



