FERNS. 



177 



Big. 215. 

 Spore of Pteris serru- 

 lata showing the three- 

 rayed elevation along 

 the side of which the 

 spore wall cracks during 

 germination. 



vicinity of ferns, we would probably find tiny, green, thin, heart- 

 shaped growLhs, lying close to the substratum. These are also 

 found quite frequently on the soil of pots in plant conservatories 

 where ferns are grown. Gardeners also in conservatories usually 

 sow fern spores to raise new fern plants, 

 and usually one can find these heart-shaped 

 growths on the surface of the soil where 

 they have sown the spores. We may call 

 the gardener to our aid in finding them in 

 conservatories, or even in growing them for 

 us if we cannot find them outside. In some 

 cases they may be grown in an ordinary room 

 by keeping the surfaces where they are 

 growing moist, and the air also moist, by 

 placing a glass bell jar over them. 



366. In fig. 214 is shown one of these growths enlarged. 

 Upon the under side we see numerous thread-like outgrowths, 

 the rhizoids, which attach the plant to the substratum, and which 

 act as organs for the absorption of nourishment. The sexual 



organs are 

 borne on the 

 under side also, 

 and we will 

 study them 

 later. This 

 heart-shaped, 

 flattened, thin, 

 green plant is 

 the prothallium 



of ferns, and we should now give it more careful study, be- 

 ginning with the germination of the spores. 



367. Spores. — We can easily obtain material for the study of 

 the spores of ferns. The spores vary in shape to some extent. 

 Many of them are shaped like a three-sided pyramid. One of 

 these is shown in fig. 215. The outer wall is roughened, and 

 on one end are three elevated ridges which radiate from a given 



Fig. 216. 

 Spore of Adiantum 

 acrostichoides with 

 winged exospore. 



Fig. 217. 

 Spore crushed to remove exospore and 

 show endospore. 



