251 BOTANICAL GAZETTE. 



of a leaf of Nymphica, cut parallel to its surface, and examine it as a 

 transparent object (still better if we illuminate it with polarized light) 

 we shall see that these internal hairs, like external ones, are associat- 

 ed with the fibrovascular system ; and toward the margin of the leaf, 

 where the tissues are thin and the veins small, we shall find that the 

 hairs exist only upon the veins and not between them. This is quite 

 in accordance with what we know of the habit of all hairs, as I have 

 already explained. 



If we take a transverse section of the leaf of Nyvip/uva or Nu 

 phar\ cut across the midrib, we shall be struck by another fact con- 

 necting these internal hairs with the epidermal system. We 

 shall at once notice that from the upper side of the leaf — which is, 

 under common circumstances, the only side exposed to the air, and is 

 consequently the only side possessing a true epidermis — these hairs 

 spring like stumps of trees in an inverted field. From end to end of 

 the section they will be observed planted close together, their pedicels 

 imbedded in or forming a part of the epidermal layer, and their 

 branches spreading downward and inward through the underlying 

 parenchymal tissue. This is very marked in stained sections, in which 

 the hairs ta'ce a darker color than the surrounding tissues ; but in an 

 unstained section, polarized light differentiates the structures quite as 

 well as the elaborate, double staining process now so commonly em- 

 ployed. It is to be noted that this arrangement of the hairs is con- 

 fined to the upper or epidermal side of tlie leaf, and that no similar 

 arrangement is to be seen at any other part. The distribution of the 

 hairs on the interior of the petiole of the water jjlants is somewhat 

 different from their arrangement on the interior of the leaf, but it is 

 closely analogous to the arrangement of hairs upon the exterior of the 

 petiole of land-plants. 



I have referred to the fact that these internal hairs are good ob- 

 jects upon which to use polarized light ; and this is a point of no small 

 importance in the argument for their being actually hairs. To any one 

 acquainted with the behavior of vegetable tissues with 

 the polariscope, particularly of vegetable hairs, the manner 

 in which these internal structures of the Nymplmaceoc are 

 affected by polarized light is strong confirmation of their claim to be 

 regarded as epidermal organs and true hairs. The way in which they 

 take different colors in the process of double staining, will be another 

 affirmative argument with those familiar with that process and its 

 effects. Suffice it to say in this connection, that these internal hairs 

 behave in precisely the way, and take exactly the colors, that exter- 

 nal hairs do. 



That structures physiologically referable to the epidermal system 

 should be found growing in the midst of the parenchymal system, is 

 not altogether anomalous, for sections of the leaf and i)etal of Mai:;no- 

 lia s;yanaiflora reveal an abundance of thickened, irregular, unicellular 

 structures scattered through the parenchyma, which, both in the'r 

 appearance and in their mode of distribution, at once suggest some 

 sort of similarity to the internal hairs of Nyiuphcea and Niiphar; but 

 which, in my judgment, are parts of the glandular system of the Mag- 



