SOME TYPES OF FLOWEELBSS PLANTS. 241 



to illustrate the process of setting free oxygen, whiph accom- 

 panies fixation of carbon (§ 149), is an aquatic moss,' 



THE STUDY OF A FERN.2 



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 i^ 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 

 pinnx, each composed of many pinnules. Draw the under side of one of 

 the pinnse, from near the middle of the frond, enlargeti to two or three 

 times its natural size, as seen through the magnifying glags. 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). 



(6) The membranous covering or indusium 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-feemina. Any 

 species of Asplenium or of Aspidium is just as well adapted for study. Cystopteris is 

 excellent, hut the indusium is hard to find, folypodium vnlgare is a simple and 



