SOME TYPES OF FLOWERLESS PLANTS. 941 
to illustrate the process of setting free oxygen, which accom- 
panies fixation of carbon (§ 149), is an aquatic moss.’ 
THE STUDY OF A FERN.? 
299. Conditions of Growth. —If the specimens studied were col- 
lected by the class, the collectors should report exactly in regard to the 
soil and exposure in which the plants were found growing. Do any 
ferns occur in surroundings decidedly different from these ? What kind 
of treatment do ferns need in house culture ? 
300. The Underground Portion. —Dig up the entire underground 
portion of a plant of lady-fern. Note the color, size, shape, and append- 
ages of the rootstock. If any are at hand which were collected in their 
late winter or early spring condition, examine into the way in which the 
leafy parts of the coming season originate from the rootstock, and note 
their peculiar shape. 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. 
301. 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 consists 
of a slender axis, or 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 magnifying 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 (already seen with the magnifying glass, 
but now much more clearly shown). 
(b) The membranous covering or indusiwm of each sorus. Observe 
how this is attached to the veins of the pinnule. In such ferns as the 
common brake (Pteris) and the maiden-hair (Adiantum) there is no 
separate indusium, but the spore-cases are covered by the incurved edges 
of the fronds. 
1 Fontinalis. 
2 The outline here given applies exactly only to Asplenium filix-femina. Any 
species of Asplenium or of Aspidium is just as well adapted for study. C 'ystopteris is 
excellent, but the indusium is hard to find. Polypodium vulgare is a simple and 
