—48— 



Woodwardia Virginica Smith. Sandy cypress-swamp at Ft. 

 Lauderdale. 



Ames Botanical Laboratory, N. Boston, Mass. 



POLYSTICHUM ACROSTICHOIDES AND SOME INSECTS 

 THAT INFEST IT. 



By Augusta Schenck Kalbfleisch. 



To the frequenter of the woods and hills our native Christ- 

 mas fern (Polystichum acrostic hoides) is no doubt a familiar 

 object, but those who have never studied it closely, beneath the 

 microscope, little dream of the minute insect life hidden among 

 its sporanges. 



Its range is quite wide, and however abundant it may be in 

 rocky soil, on the banks of the Hudson and elsewhere, it never- 

 theless grows in profusion on Long Isalnd in rockless woods 

 under the shade of great chestnuts and oaks. But it invariably 

 selects hilly ground as its home and I have never found it distant 

 less than three miles from the salt water. It is most sociably 

 inclined and large patches of it are seen beside the hay-scented 

 fern (Dicksonia pilosiuscula) and silvery spleenwort (Asplenium 

 acrostichoides.) 



The fronds arise in dense clumps from the stout, creeping 

 root stock, which runs horizontally through the ground a little 

 below the surface, and one would never imagine its firmness, un- 

 til a vain attempt is made to dislodge it. The stipe, brown and 

 chaffy, is from 3 inches to 7 in length. The leaves are from 6 

 inches to 2 feet long and 2 to 3 inches wide ; lanceolate, once 

 pinnate, smooth, evergreen and coriaceous. The pinnae are 

 somewhat halberd-shaped and toothed. The fertile and sterile 

 leaves are similar in form ; the fertile, however, are 

 contracted toward the summit, while the sterile fronds are rather 

 abruptly pointed. The indusium resembles a small, brown, flat- 

 tened bladder and encloses from 12 to 15 sporanges which are 

 scattered when the indusium breaks. The sporanges are round 

 with a vertical ring which bursts transversely and releases the 

 great mass of spores, which are small and white. Each sporange 

 is furnished with a pedicel about three times its own length. 



