178 Transactions. 



The sections Inundata and Cernua comprise comparatively few species. 

 The species which belong to the former are fairly widely distributed, but 

 are confined to boggy and marshy habitats. I venture to propose that the 

 composition of the Cernua section as arranged by Baker, and by Pritzei 

 following him, should be altered in accordance with our increased know- 

 ledge of the main characters of the species which have hitherto been 

 included in it, certain of these species, such as L. densum, L. voluhile, and 

 possibly L. ohscurum and L. casuarinoides, being removed to the section 

 Clavata, while L. ramulosum, and possibly also L. diffusum, should be 

 removed from the latter section and placed near to L. cernuum. This 

 suggestion has been previously made by me (16, p. 301). 



The reason for this is that the cernimm type of prothallus, a protocorm 

 stage in the embryo plant, and the " mixed " type of stelar structure 

 undoubtedly go hand in hand, and that although the species which show 

 these characters do not altogether show a close similarity in general habit 

 of growth and in external form, yet the presence of the hrst-named charac- 

 ters should be given chief position in determining the limits of the Inundata 

 and Cernua sections. Now, Baker and Pritzei in their classifications of the 

 genus have both described the species L. cernuum and L. densum as upright, 

 tree-like forms. This is quite misleading. It is only the lateral branches 

 in these two species which are erect. There is a trailing main stem which 

 in the case of the former species is snake-like in growth, spreading above- 

 ground for as much as 12 ft. to 15 ft. in a series of loops, and rooted 

 to the ground at each node, and in the case of the latter species is a 

 subterranean rhizome which attains an extreme length of 8 ft. to 10 ft. 

 The species L. laterale also, which is placed near L. cernuum by Pritzei, 

 is described by him as nearly or quite erect. This also is an incorrect 

 description, for whereas the aerial branches are more or less erect, the main 

 stem is a short much-branched underground rhizome which ramifies exten- 

 sively in the soil. One rather suspects that the supposed upright habit 

 of growth of these species has been one of the reasons which led the two 

 systematists into grouping together such really widely different species as 

 L. cernuum and L. densum. For the same reason, the great point that is 

 made by Jones (21, p. 32), that " the fact must not be overlooked that the 

 banded structure is well marked in the stem of the erect-growing species of 

 L. ohscurum,'" likewise loses its significance in view of the fact that in this 

 species also the main stem is subterranean and creeping, and that it 

 undoubtedly belongs to the Clavata section. The type of prothallus and 

 voung plant and also the stelar anatomy of L. densum and L. voluhile 

 indicate that these species, as well possibly as the two species L. ohscurum 

 and L. casuarinoides, should be included in the section Clavata. This, then, 

 would leave in the Cernua section only the type species L. cernuum with all 

 its varieties, and the species L. laterale with its congeners L. ramulosum 

 and L. diffusum. 



The fact that one or two species in the Inundata section — e.g., L. con- 

 textum Mart, and L. cruentum Spring — show the Selago habit in the fertile 

 legion is open to various interpretations. Either they have preserved 

 unaltered a phylogenetic character ; or perhaps it is an indication that 

 the whole genus is really to be read as a reduction series, and that in these 

 particular species, as also in the case of the New Zealand plant L. Billardieri 

 var. gracile, mentioned above, actual transitions in the process are to be 

 seen. However, isolated instances such as these are not to be interpreted 

 apart from the main evolutionary tendencies to be observed in the genus 

 as a whole. 



