GERMINATION OF FERN SPORES. 1 9 



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 micro- 

 scopic, and many are of such a shape that they do not appear 

 uniform owing to the various directions from which we view 

 them. 



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

 credible. Lindley calculated that a single frond of Scolopeii- 

 driuiii produced about 80 sori, with an average of 4500 sporan- 

 gia in each sorus, and each sporangium containing 50 spores, 

 making a total of 18,000,000 spores. The copious green spores 

 of Osinunda cinnaiiionwa, or the pale-yellow, powdery spores of 

 a well-developed specimen of BoirycJiiiim Vir-gtuiatium, must 

 far exceed this computation. By drying either of these species 

 under pressure between sheets of paper great quantities of the 

 spores may be obtained for examination. Specimens for this 

 purpose should be selected just before the sporangia reach 

 their maturity. 



CHAPTER IV. 

 GERMINATION OF FERN SPORES. 



Alle Glieder bilden sich aus nach ew'gen Gcsetzen, 



Und die seltenste Form bewahrt im Geheimniss das Urbild. 



-Goethe. 



6 1 . The germination of the fern spores usually takes place 

 a considerable time after they are discharged from the sporangia, 

 but in Osmunda, which develops its fruit early in the season, 

 they commence their growth only a few days after dissemination. 



62. Thalloid Phase. — In germination the exospore splits 

 along the side, and the protruding endospore, sometimes with 

 its divisions already formed by septa or partitions, forms, not 

 a fern, but a thalloid structure resembling one of the lower 



