—72— 



tries from which they were brought ? these authors would 

 unhesitatingly pronounce the plants O. vulgatnm" 



Texture. In its major features, texture is a fairly 

 constant character, and might have been included among 

 those of diagnostic value. Indeed, in so far as the prime 

 divisions are concerned, the plants are practically unva- 

 rying. Coriaceous fronds never vary to papyraceous, 

 and neither of these to herbaceous. It is possible for thin- 

 fronded plants subjected to undue exposure to become 

 thickened, and this must be taken into account. All are 

 familiar with the appearance of shade ferns after expo- 

 sure to the sun. One of the best instances is found in 

 W oodsia obtusa, which in shade is a fairly lax plant, 

 green in color, but in sun becomes erect and yellowish, 

 with thicker fronds. 



Yestiture. The amount of scales, hairs, glands, etc., 

 upon a frond is usually proportionate to the amount of 

 exposure to which it is subjected. In moist regions, 

 ferns are usually smooth ; in dry regions, clad with farina, 

 wool, glandular hairs, scales, etc. Intermediate condi- 

 tions plainly have their effect. The common Woodsia 

 obtusa in direct sunlight becomes densely glandular- 

 hairy, and the same thing is characteristic of Dicksonia 

 pilosiuscula. Both Prof. Peck and Prof. Eaton have 

 named forms of Nephr odium Noveb or accuse because 

 the pubescence was greater than usual. The principal 

 distinction of the plant named Nephrodium aquUonarc is 

 a heavier clothing of scales. It can scarcely be specifi- 

 cally distinct from N. fragrans. 



Cutting of the Frond. Frequently the outline and 

 cutting of the frond are considered of equal importance. 

 This, to my mind, is a great mistake. The outline of the 

 frond remains practically unchanged, while the serration 

 or lobing varies with the situation in which the plant 

 grows. Even a change in the shelter may alter the ser- 

 ration, as we see in the case of Polystichum acrosti- 

 choidcs f. incisum. It cannot be denied that the cutting 

 often makes a great difference in the appearance of cer- 

 tain species, notably in Botrycluum ternatutn, but appear- 



