THE ANATOMY AND AFFINITY OF STROM ATOPTERIS MONILIFORMIS, ME'L'T. 141 
interpretation as organs of absorption. If it could be finally established that the 
mature sporophyte is almost or entirely rootless, the latter view of these organs 
would be greatly strengthened. But in the absence of certainty regarding roots, 
the cortex of the stem is deserving of special comment. It is sclerotic and composed 
entirely of brown-walled fibrous elements, bearing many large oval pits on all their 
thickened walls (text-figs. 14, 15). In the mature cortex there are no intercellular 
spaces, and even in the cortex of the immature stem intercellular spaces are few and 
very small. But further, while the still thin-walled cells of the immature cortex 
possess delicate protoplasts, the thick-walled pitted cells of the mature cortex seem 
entirely devoid of protoplasts. The presence of pitted thick-walled fibrous elements 
and the absence from these of intercellular spaces are common features of the cortical 
Text-fig. 12. Text-fig. 13. 
tissues of ferns ; but if Stromatopteris is rootless, and absorption is conducted by 
the general stem-surface, or by dermal appendages, the empty cortical cells may 
be regarded as a supplementary conductive system, rather than as a storage or 
mechanically effective zone. 
The dermal appendages of ferns can seldom be relied upon in systematic deter- 
minations ; for while in a general sense the simple hair is usually considered a 
primitive, structure, and the massive scale derivative or advanced, it is recognised 
that the peculiar life conditions of any organism may determine to a greater or less 
extent the types of appendages developed. Within the genus Gleichenia itself 
variations in this respect are found ; for while Gl. pectinata and Gl. lineata have 
hairs alone, Gl. simplex has scales, while Gl. circinata has both hairs and scales. 
The simple hairs and massive scales of Stromatopteris may then be matched from 
the genus Gleichenia, and the transitional types may be regarded as expressive of 
peculiar physiological conditions ; but the absence of hairs or scales would not of 
necessity alter the general relationships of these organisms. 
With the conical emergences, however, the case seems different. Such emer- 
gences are uncommon, but they are characteristic of certain Gleichenias. They 
TRANS. ROY. SOC. EDIN., VOL. LII, PART I (NO. 6). 23 
