Xl 
common occurrence, Pt. cretica for instance, and due to 
inversion of margin, but a change of form, as in Drynaria 
(polypocliimi) when the sterile frond resembles a withered 
oak leaf, Onoclcea, Cryptogramme,, Lomaria, and many 
Acrostichums ; among these also an intermediate differ- 
ence is sometimes seen, as in A. variabile and quercifolium. 
It must not be forgotten that young fronds sometimes 
vary developmentally in shape and colour from the type, 
as Woodwardia radicans. Fronds are also often affected 
by their locality ; Ad. caudatum exposed to the sun is 
coriaceous, under the next bush, subcoriaceous or herba- 
ceous;. and the cutting is much deeper in the former 
position. Plants in certain situations cease to be farinose 
as they develop, also with diminished cutting, as Cheil- 
lanthes farinosa, the Ch. Dalhousise of higher rock, where 
it grows more luxuriantly. Frond and stem are measured 
separately. 
15. A change of cutting affects venation (§ 17) by 
the division not descending to lowest veins, which there- 
fore unite in. arches, Pteris quadriaurita thus probably 
assumes a' so called Campteriod form as pt. (compt.) biau- 
rita ; a mode of variation which may also possibly extend 
to other plants at present reckoned as species, as Aspl. 
ceterach and alternans, &c. Whenever therefore an ab- 
normal form is found affecting all the fronds of a plant, 
anything unusual in its surroundings should be noted, and 
its neighbourhood searched for intermediate stages of 
development. There is an obscure fern Psilodochea 
salicifolia, reported to have been found near Lahore, like 
