9i 
a new genus of Pontederiaceae. 
bracts with the included flowers are about in. long, the ripe 
carpels, including the styles, tV - i in., and the seeds TnrrV in* 
Referring to the most recent monograph of the Ponte- 
deriaceae, that of Solms-Laubach in the fourth volume of 
Alphonse de Candolle’s Monographs, it is evident that Hydro- 
thrix must be regarded as either a section of the order, or as 
an aberrant member, characterized hy foliage, inflorescence 
and the solitary stamen. Hitherto it has not been usual in 
taxonomic works to segregate individual genera as aberrant, 
even when monotypic, but rather to elevate them into repre- 
sentatives of tribes or suborders. If conceded that aberrant 
genera should be universally appended as such to the order 
of which they are regarded as members, it is impossible to lay 
down any rules as to the number or value of the characters 
that should entitle them to such local dissociation. Much 
must depend on the homogeneity or the contrary of the other 
members of the order, and something on the extent of the 
aberrant genus. Were Clematis monotypic (that is consisting 
of one species only), it might be better considered as an 
aberrant Ranunculaceous genus ; but whereas it contains many 
species distributed over all the continents, and these form 
a very considerable proportion of that order, its claims are 
irresistible to be regarded either as a tribe, or as a separate 
order. The matter resolves itself into a question of con- 
venience or expediency. Nymphaeaceae, in its larger sense, 
consists of six oligotypic genera, all of which are aberrant 
in respect of the seventh, the assumed type, Nymphaea. 
Hamamelidae 1 is another order of heterogeneous contents; 
it consists of about twenty genera, of which none have more 
than three species. But whereas in Nymphaeaceae the seven 
genera are all grouped under three tribes so distinct as to 
be considered orders by some, of Hamamelidae no genus 
can be considered more aberrant than another, nor can they 
1 To the fifteen genera of this order, described in the ‘Genera Plantarum’ in 1865, 
there are now to be added Disanthus , Maxim., Davidia, Baill., Ostrearia , 
Baill., and Maingaya , Oliv. On the other hand, Tetrathyrium : Benth., falls into 
Loropetalum . 
IT % 
