436 WILLIS : MORPHOLOGY OF THF FODOSTBMACEÆ 
already described. Passing on a stage further, Ave come to 
the Lophogynes and Apinagias, which have strongly marked 
dorsiventrality in the vegetative organs, especially in the 
secondary shoots. Here, as in Tristicha hypnoides, we find 
the flowers again showing zygomorphism, in that the 
stamens on the upper side are suppressed, as compared with 
the radial flowers, and the upper stigma is often smaller 
than the lower. 
From these we pass to the Eupodostemeæ, all of which 
show a very high degree of dorsiventrality in the vegetatiA^e 
organs and also in the floral, but the rule indicated above 
seems to hold throughout, that the dorsiventrality is most 
marked in the vegetative organs, and shows less or later in 
the floral shoot, spathe, stamens, stigmas, ovary, and fruit, 
in the order named. Thus in Dicræa there is a highly 
dorsiventral thallus, the growing point, as well as the other 
morphological and anatomical features, showing the asym- 
metry about the horizontal plane, but the secondary shoots, 
though reduced, still stand comparatively erect until late in 
their life, so that the earliest stages in the floral develop- 
ment, or the impulses to that development, perhaps occur 
at a time Avhen the shoot is still not prostrate. The flower 
is extremely dorsiventral, and the upper stigma is smaller 
than the lower, but the fruit is isolobous. The flower, 
though horizontal or nearly so in the ripe bud, bends 
upwards and stands erect as soon as the spathe opens. 
The bracts and spathe both exhibit differences of structure 
betAveen their upper and lower sides, but much less marked 
than in some of the succeeding genera ; the difference is 
most marked in the most prostrate shoots, 0.^., in D. stylosa. 
In Podostemon and Mniopsis the general characters are 
much the same, but the secondary shoots are longer and 
with marked structural dorsiventrality from the very first. 
The flowers emerge in a comparatively erect position, but 
show more zygomorphism than in Dicræa, in that the 
ovary is often rather larger in the upper than in the lower 
loculus, Avhile the fruit, though erect, is ahvays anisolobous. 
