256 The Scottish Naturalist. 



the belief that the development of this peculiar group of cells has 

 much to do with the deciduousness of the leaves. In No. 1 this 

 group is least developed, and shows itself merely in the narrow 

 interval between the nerve and the sloping base of the large 

 rectangular cells, which occupy much the larger portion of the ex- 

 panded bases of the leaves. 



In No. 2, bordering on No. 1, but a little further inwards from 

 the light, the moss is quite as robust, and the leaves are not 

 deciduous ; but they are less falcate and are decidedly so only 

 near the apices of stems. The bases are expanded and the 

 auricles are more manifest and have cells with a reddish tinge 

 here and there. In almost ail instances where the leaves are 

 straight the spinous condition of the back of the arista near the 

 apex is shown. 



No. 3 is similar to No. 2, but the leaves have a slight tendency 

 here and there to become deciduous, and the spinous condition of 

 the arista is more obvious. The upper margin of the expanded 

 base is still entire. 



No. 4 is similar to No. 2 and equally robust, but the leaves are 

 scarcely at all falcate. The bases of the leaves are much, and 

 even suddenly, expanded, and their upper margin is serrated. 

 The arista is closely spinulose on the back as in D. aristatum. The 

 leaves are slightly deciduous. 



No. 5 slender ; the leaves are nearly straight and more decid- 

 uous. Nerve broader, being one-third breadth of base. Arista 

 quite as in D. aristatum. 



In No. 6, the arista bears spines on the back only here and there. 

 The auricles are better developed and more lateral. 



No. 7 is slender. Auricles much developed, even bulging at 

 times beyond the marginal base, and hollow. Arista more spinu- 

 lose than in the preceding. 



No. 8 with apices of stems often bare of leaves, and stump- 

 like as in D. lo?igirostre, and otherwise having almost all the 

 characteristics of this moss. The auricles are now much de- 

 veloped, and the arista is smooth (not spinulose) on back, and 

 toothed only near the apex. Perhaps the base of leaf is rather 

 more expanded than in D. lougirostre. 



It is noticeable in this series that those leaves whose bases have 

 been previously detached from the stem have few or none of the 

 spinulosities so manifest on many of those still firmly adherent 



