36 Our Native Ferns. 



verse slit to discharge their copious sulphur-yellow spores. The 

 veins of the sterile portion of the plant copiously anastomose. 

 64. Botrychium. — In the grape-ferns the sporangia are glob- 

 ular and arranged in double rows along the narrow segments, 

 more or less in panicles. The veins are free in all the species, 

 yet in the smaller, fleshy ones this may not be readily perceived. 

 65. Spores. — The spores of ferns constitute the fruit proper. 

 A spore consists of two distinct closed sacs and the cell contents, 

 all of which differ from each other in chemical composition. The 

 outer layer (exospore) consists chiefly of cellulose; the inner 

 layer (endospore) contains some albuminous matter in addi- 

 tion, while the cell contents consist chiefly of a thin, colorless, 

 jelly-like substance known as protoplasm, with grains of chloro- 

 phyll (the green coloring matter of plants), starch and oil. The 

 exospore may be smooth or roughened by points, granules, warts, 

 or prickles. The shape varies with different species yet all are 

 rounded, and most are oblong or at least longer than broad. All 

 are microscopic and many are of such a shape that they do not 

 appear uniform, owing to the various directions from which we 

 view them. (Fig. 15-22). 



Fig. 15-22. Spores, highly magnified. Cryptogramine acrostichoides, R. Br., Lygo- 

 dium palmatitm. Swz., CysUypterU Jragilis, Bernh., Schissea pudlla, Pursh. 



Acrostwhym mirernn, L., Polypodium Califomicuin, Kf., Gymnogramme iriangu- 

 larls, Kf., Not/iolama Candida, Hoolv. (Original.) 



66. The number of spores produced by a single fern is in- 

 credible. Lindley calculated that a single frond oi Scolopendrium 

 produced about 80 sori, with an average of 4500 sporangia in each 

 sorus, and each sporangium containing 50 spores, making a total 

 of 18,033,000 spores. The copious green spores of Osmunda cin- 

 namomea or the pale yellow, powdery spores of a well developed 

 specimen of Botrychium Virginianum must far exceed this com- 

 putation. 



