OF CEYLON AND INDIA. 
453 
the other characters of the flowers and fruit, &c., are so 
simple, that one must regard the order as representing an 
old phylum of true Dicotyledons, The next question that 
arises is whether it has descended from aquatic or terrestrial 
ancestors. On the whole, considering the terrestrial type 
of both flower and fruit, the latter seems most probable. 
A possible origin for the order seems to be from plants 
already growing on the banks of mountain rivers, with 
creeping adventitious roots upon which secondary shoots 
were regularly developed. We can imagine these plants 
“ taking to the water ” by means of these shoots, which in 
the intermediate period of transition would have to be more 
or less amphibious. Possibly the anatomical difference 
between the primary axis and the secondaries may indicate 
that the latter became adapted to the new existence sooner 
than the former. . We do not yet, however, so far as I am 
aware, know to what extent primary and secondary axes 
differ in other plants. The anatomy of the primary axis in 
the few Podostemaceæ yet examined is moi’e like that of 
other water plants than that of the secondaries, which 
perhaps indicates the origin of the order from some form 
akin to the Nymphæaceæ or other ancient group of water 
plants, far back in the evolution of the Dicotyledons. 
Tl%e Systematica Pesitiaii tiie Pedastemaeeæ. 
This also is a question for further discussion when fur- 
ther evidence shall be available. The family is very isolated, 
like so many other groups of submerged water plants. In 
our present ignorance of the phyla of the evolution of the 
higher plants, the most we can hope to do is to trace some 
line of apparent descent near to which we may place the 
order. I have already indicated"' that I regard the Sym- 
petalæ, as do many other authors, as polyphyletic ; one of 
the lines of their phytogeny seems to me to run through the 
neighbourhood of the Englerian cohorts Rosales, Myrtifloræ, 
* Manual and Dictionary, vol. I., p. 68. 
