NEPHRODIUM DELTOIDEUM 



BY WILLARD N. CLUTE. 



When the collector finds his first specimen of 

 Nephr odium deltoideum he can hardly believe that he 

 has found a perfect frond. The small green ears that 

 parallel the rachis in the lower half of the frond are so 

 unlike the other pinnae and the break between the two 

 forms is so sudden and emphatic that it seems easier 

 to assume that these stubby pinnae have been stunted, 

 as the result of injury by fungi or insects. Further 

 search, however, only results in the discovery of more 

 fronds of exactly the same pattern, and convinces the 

 collector that he has in hand one of the most curious 

 of the wood ferns. 



Nephr odium deltoideum is a native of the West 

 Indies where it grows on the wooded foot hills much 

 as our common wood-ferns grow in the forests of the 

 Eastern United States. When only the upper half of 

 the fronds is seen the fern has no special individuality. 

 It is likely to remind the observer of the common 

 marginal shield fern {Nephr odium marginale). But 

 once the whole frond is brought into view its very 

 characteristic from makes it a well-marked species and 

 one that even the novice cannot go astray in identify- 

 ing. Although its allies give some indication of 4 re- 

 duction of the lower pinnae in their fronds there ap- 

 pear to be none in which the departure in this direc- 

 tion is half as strongly emphasized. 



Like practically all the ferns in which the chloro- 

 phyll-bearing tissue is reduced in the lower half of the 

 frond, the leaves are produced in circles. The reduc- 

 tion in leaf surface is regarded as an adaptation to light 

 conditions since the upper pinnae are likely to shade 

 those below, but the reduction may have been brought 



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