A Dictionary of Choice Ferns. 
315 
PTERIS — continued. 
opposite; the upper ones are simple and 4in. to 6in. long, 
wiiile the lower oEes aro' provided with several long, narrow 
leafits on each side ; the edge of the barren ones is con- 
spicuously saw-toothed, and the fertile ones show a narrow 
involucre of a parchment-like texture covering the spore 
masses. Fter'is serrulata is extremely variable, and through 
its variations it is brought into close connection with 
P. cretica. C'ristation is the form of variation which, as 
a rule, is most noticeable. P. s. cristata is a variety whose 
fronds, instead of being lengthened into a terminal leaflet, 
have a more or less rounded form, produced through the 
cristation of the leaflets, which appear to be all of nearly 
equal length. The original P. s, cristata is of upright habit 
(Fig. 120), but many seedlings raised from it have a more 
or less drooping character. Other fine forms are P. s. 
gloriosa (with a fan -like crest), P. s. gracilis, and 
P. 8. undulata. 
P. tremula. 
This strong-growing, greenhouse species, commonly 
called the "Australian Bracken," has become a very popular 
Fern. Its ample fronds, 2ft. to 4ft. long and quite 2ft. 
broad, are borne on strong, upright, naked, bright chestnut- 
brown stalks 1ft. to 2ft. long. Besides the terminal leaflet, 
which consists of a few closely-placed, entire lobes, there 
are, according to the size of the fronds, from four to six 
pairs of lateral leaflets c The upper leaflets are simply 
pinnate, with entire leafits on each side, the largest being 
about Gin. long and more than lin. broad; the lower ones 
are often very compound, sometimes 1ft. long, and twice 
divided to the midrib. The fronds are of a soft, papery 
texture, bright green in colour, and naked on both sides. 
The abundant spore masses are of a pronounced reddish- 
brown colour, and sometimes fill up the whole of the leafits 
except the midrib. There are numerous varieties, but none 
that call for special notice. P. t. elegans is a light and 
elegant crested form of drooping habit, smaller than the 
type ; P. t. Smitheana, another fine crested form, very com- 
pact; and P. t. Variegata has its pinnae variegated with 
silvery white. 
PYCNOPTERIS. See Nephrodium. 
RHIPIDOPTERIS. See Acrostichum. 
SADLERIA. 
Two species of stove Ferns of tree-like habit go 
to form this genus. Only one — S. cyatheoides — has 
