428 WILLIS : MORPHOLOGY OF THE PODOSTEMACBÆ 
to them, and indeed this is probably very often the case. 
Here, however, we meet with the most extreme known 
zygomorphism in a group the flowers of which are wind- 
er self-fertilized, stand erect, and are very inconspicuous 
and not visited by insects. The dorsiventrality of the 
flowers seems, as will be discussed below in detail, to have 
been acquired at the same time that the flowers were pro- 
gressing in the direction of increased anemophily and 
autogamy, and appears to be of absolutely no use to them, 
except in so far as it represents a reduction of the amount 
of material expended upon the construction of the floral 
organs. The more dorsi ventral the flowers the more de- 
graded their type, on the whole ; they have, as compared 
with the higher American types, lost much of the certainty 
of the cross-fertilization, and gained little or nothing in 
certainty and abundance of seed, but only in reduction of 
material. However dorsiventral the flower becomes it still 
stands erect as long as it possesses a stalk, and when at last 
we come to the forms without the stalk we find the flower 
curving its ovary and stamens so as to get them as erect 
as possible. It seems as if the flower were, so to speak, 
struggling against the dorsiventrality to the last, and doing 
its best to try for a cross, even when the chance of such a 
thing has sunk to a very small figure. 
It is difficult to resist the conclusion in looking at these 
flowers that the dorsiventrality which is the most marked 
feature of the order as a whole is not only no advantage to 
them, but is an actual disadvantage, against which they 
struggle, making various compromises, but always tending 
more and more in the direction of regular autogamy, which 
at last is adopted outright in Podostemon Barberi and 
possibly in other forms. 
In the fruits of these plants we get perhaps even a clearer 
illustration of the general principle now under considera- 
tion. The ifruit in this order is evidently a “land” fruit, 
and seems quite unsuited in itself or in the seeds for an 
aquatic existence ; it shows no such adaptations as we may 
