MAIDENIA ; NEW GENUS OF HYDROCHARIDACE^ 315 



Queensland, differs from the typical species of the genus in having 

 an elongated leafy stem with the habit of a Potamogeton but quite 

 unlike that of Maidenia. 



One of the specimens of Maidenia bears the remains of a 

 stolon springing from the base of the stem; this indicates a method 

 of propagation comparable with that of Vallisneria spiralis. The 

 presence of more than one flower in the leaf-axil in the female 

 plant of Vallisneria also suggests a comparison witli the com- 

 plicated and much reduced leaf- and flower- bearing axillary shoots 

 in Maidenia. 



The floral structure is that of Vallisneria but greatly reduced. 

 The typical floral plan of the family Hydrocharidace£E is trimerous; 

 the perianth consisting of two alternating whorls, the relative size 

 and importance of which varies in different genera. In Lacjaro- 

 sipJion the inner and outer whorls are very similar, but in 

 Vallisneria the members of the inner are reduced in the female 

 flower to inconspicuous scales, while in Maidenia the reduction is 

 carried further and there is no external trace of an inner whorl. 

 One or more series of staminodes is often present in the female 

 flower in this family ; in LagarosipJion there is generally a whorl 

 of three, but in Vallisneria, as in Maidenia, no staminodes occur. 



The male flower of Maidenia shows an extreme case of reduc- 

 tion. In the other genera of the family there is a trimerous 

 perianth, generally represented by an inner and outer series, as in 

 Lagarosiplwn ; in Vallisneria the inner series is absent. In the 

 family as a whole there are from ] to 5 whorls of stamens, some 

 of which may l)e staminodial as in Lagarosiplwn ; Vallisneria is 

 exceptional in having one wdiorl only, one or two members of 

 which are sometimes infertile. The male flower of Maidenia 

 shows a further and striking reduction as it consists merely of a 

 single stamen with no trace of perianth or other structure. A 

 resemblance to Lagarosiphon and Vallisneria is also found in the 

 few and proportionately large pollen-grains. The slight indication 

 of zygomorphy is also of interest in view^ of the comparison with 

 the flower of Vallisneria. 



To recapitulate : the female flower of Maidenia closely resembles 

 that of Vallisneria ; there is a slight reduction in the complete 

 disappearance of the inner perianth w^iorl. The male spathe 

 resembles in external form that of Vallisneria, but contains, in 

 place of a stout central axis bearing numerous flowers with 

 trimerous symmetry, merely a slender axis bearing numerous 

 stamens. 



The position of the new genus is clear. It belongs to the 

 subfamily Vallisnerioideae, and in this subfamily to the tribe 

 Vallisneriese, of which hitherto we have known only two genera, 

 the African Lagarosiphon and the almost cosmopolitan Vallisneria. 

 The latter genus is represented in AustraHa by V. spiralis and two 

 little known species endemic in Queensland, V. gracilis Bail., 

 closely allied to V. spiralis, of which it has the appearance of a 

 dwarf form, and the imperfectly known V. caulescens. 



The genus is named after Mr. J. H. Maiden, Director of the 



