ASPIDIUM. 119 



not by an endoderm but by the cambium which builds 

 up fibro- vascular bundles of the open collateral type. 

 Phloem is on the outside, xylem on the inside. (Rheum 

 makes a curious exception to this general rule, for in it an 

 anomalous growth is seen, the xylem growing outside the 

 phloem.) 



The number of bimdles varies considerably and also the 

 elements that go to make up xylem and phloem. 



The centre of the stem is occupied by a pith made up in 

 the main of suberized cells. 



ASPIDIUM. 



Aspidium (Male-fern) is the rhizome of Dryopteris 

 Filix mas, Schott, and of Dryopteris marginalis, Asa Gray 

 (nat. ord. Filices), U. S. 



The first-named plant, also known as Aspidium Filix- 

 mas. Poly podium Filix mas, L., Polystichiim Filix mas. 

 Roth, Nephrodimn Filix mas, Mich., Lastrea Filix mas, 

 Presl., grows plentifully in both forests and plains through- 

 out the temperate portions of Europe and Asia. In 

 North America it is rarer, growing in the mountains of the 

 western part of the continent. 



The less reputed but probably as valuable Dryopteris 

 ntarginalis is found in the eastern portion of the continent. 



For a non-tropical fern the plant is fairly large. The 

 rhizome is thick and scaly. From it arise the fronds in a 

 circular tuft; below, it sends down innumerable fibrous 

 roots. It is collected in autumn and should not be used 

 if more than a year old, or when it has lost its internal 

 green color. 



The rhizome is collected when the reserve products are 

 in abundance, this being about the latter part of the 

 summer. D. marginalis is hardy in New England, 

 remaining green a greater part of the winter ; thus it uses 

 up, during the winter, much of the stored food products 

 which are formed in the spring and midsummer. The 



