TYPES OF CRYPTOGAMS; PTERIDOPHYTES 245 
This kind of vernation is decidedly characteristic of ferns. Observe 
the number and distribution of the roots along the rootstock. Bring 
out all these points in a sketch. 
314. The Frond. — Fern leaves are technically known as fronds. 
Observe how these arise directly from the rootstock. 
Make a somewhat reduced drawing of the entire frond, which con- 
sists of a slender axis, the rhachis, along which are distributed many 
leaflets or pinne, each composed of many pinnules. Draw the under 
side of one of the pinne, from near the middle of the frond, enlarged 
to two or three times its natural size, as seen through the magnify- 
ing glass. Note just how each pinnule is attached to its secondary 
rhachis. 
Examine the under side of one of the pinnules (viewed as an 
opaque object without cover-glass) with the lowest power of the 
microscope, and note: 
(a) The « fruit-dots” or sori (Fig. 171, B) (already seen with the 
magnifying glass, but now much more clearly shown). 
(b) The membranous covering or indusium of each sorus (Fig. 171, 
C). Observe how this is attached to the veins of the pinnule. In 
such ferns as the common brake (Pteris) and the maidenhair (Adi- 
antum) there is no separate indusium, but the sporangia are covered 
by the incurved edges of the fronds, 
(c) The coiled spore-cases or sporangia, lying partly covered by 
the indusium. How do these sporangia discharge their spores ? 
Make a drawing, or several drawings, to bring out all these points. 
Examine some of the sporangia, dry, with a power of about 50 
or 75 diameters, and sketch. Scrape off a few sporangia, thus dis- 
engaging some spores, mount the latter in water, examine with a 
power of about 200 diameters, and draw. 
315. Life History of the Fern.— When a fern-spore is sown on 
damp earth it gradually develops into a minute, flattish object, 
called a prothallium (Fig. 172). It is a rather tedious process to 
grow prothallia from spores, and the easiest way to get them for 
study is to look for them on the earth or on the damp outer surface 
of the flower-pots in which ferns are growing in a greenhouse. All 
stages of germination may readily be found in such localities. 
Any prothallia thus obtained for study may be freed from parti- 
cles of earth by being washed, while held in very small forceps, in 
