TYPES OF CRYPTOGAMS; PTERIDOPHYTES 



293 



above groiznd insert here any evident points of comparison. Do you 

 find any special forms of stem development suited to a special pur- 

 pose ? Are there any organs in tie nature of leaves ? 



Fig. 213.— a Soouring-Eush (Equisetum aylvaticum). At the right is a 

 colorless fertile stem, in the middle a green BterUe one, and at the 

 left a green fertile one. 



