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THE FERN BULLETIN 



eluding Ophioglossum, Botrychium, Marsilia, Sal- 

 vinia, Azolla, Osmunda, Lygodium, Schizaea and Cer- 

 atopteris. Often the identical species with which we 

 are most familiar are listed. Some idea of the great 

 variety of tree-ferns that occur may be gained from 

 the fact that 101 species of Cyathea (including He- 

 mitelia and Alsophila) are listed. Not the least valu- 

 able part of the work are the twenty-one full page 

 plates illustrating each genus treated. 



Tree Ferns — The development of an erect trunk 

 and consequent formation of a tree fern appears to be 

 due to a constantly humid condition of the atmosphere 

 being maintained as then the roots springing from the 

 bases of new fronds are not starved. Most of the 

 crown-forming ferns maintain life in their old caudices 

 to a distance from the growing terminal. Some display 

 a tendency to raise the caudex perpendicularly while 

 others push it horizontally. Our Lastrea pseudo-mas 

 cristata, a variant of the tough evergreen species L. 

 filix-mas has formed in my collection an erect trunk 

 eighteen inches high under glass and this being wetted 

 whenever the plant is watered has at the present time 

 no less than 28 four-foot fronds forming a good speci- 

 men of the British tree fern. By the way few tree ferns 

 produce thorns on the caudex. Your article gives one 

 the impression that it is a general character. What is 

 the species referred to? — Chas. T. Druery, F. L. S., 

 London, [To one who has collected among tree ferns, 

 Mr. Druery's question about the thorns will be aston- 

 ishing. Hemitclia horrid a is so named because of its 

 stout sharp thorns and several other species have thorns 

 either on the trunk or on the stipes where they join it- 

 Almost all the American AlsopJiilas are thorny or 

 prickly as their names often indicate. Some of the 

 prickly species that come to mind at present are A. 



