2 5 6 



SEEDLESS PLANTS 



485. Part of 

 a fertile pinna of 

 polypodium en- 

 larged, showing 

 the sori without 

 indusium. 



486. Part of 

 a pinna of pellea 

 enlarged, showing 

 indusium formed 

 by the revolute 

 margin. 



the fronds or pinnae bearing them are said to be fertile. 



Are there any differences of size, shape, etc., between the 

 fertile and sterile fronds of your specimen ? 

 Between the fertile and sterile pinnae ? On 

 what part of the frond are the fertile pinnae 

 borne ? Notice the shape and 

 position of the sori, and their 

 relation to the veins, whether 

 borne at the tips, in the forks, 

 on the upper side (toward the 

 margin) or the lower (toward 

 the midrib). Look for a deli- 

 cate membrane (indnsiuni) 

 covering the sori, and observe 

 its shape and mode of attach- 

 ment. (If the specimen under 



examination is a polypodium there will be no indusium ; 



if a maidenhair (Adi- 

 ant mn\ or a bracken 



(Pteris\ it will be formed 



of the revolute margin 



of the pinna.) In lady 



fern (Aspleninm Filix- 



faemina), and Christmas 



fern (Aspidium), the sori 



frequently become con- 48? 



fluent that i <tr> oWp, 487> 488. Christmas fern (Aspidium): 



.ni, Q IS, Si J 487. part of a fertile frond, natural size; 488, 



together as to appear like a P inna enlarged, showing the sori confluent 



T j under the peltate indusia. 



a solid mass. Sketch a 



fertile pinna as it appears under the lens, bringing out 



all the points noted. 



363. The Spore Cases. Look under the indusium at 

 the cluster of little stalked circular appendages (Fig. 483). 

 These are the sporangia, or spore cases, in which the 

 reproductive bodies are borne. Seen under the micro- 

 scope each sporangium looks like a little stalked bladder 

 surrounded by a jointed ring (Fig. 484). At maturity the 



