344 Wheldon : Key to the Harpidioid Hypna. 



15. Moderately stout, frequently elongate (16). Short and obese, 

 very densely leaved, leaves large and wide {D. lycopodioides i. obesits). 



16. With many flagelliform innovations, the slender shoots re- 

 sembling D. adiincus [D. lycopodioides f. prolijerus). Without flagelli- 

 form shoots, branches resembling stems, but more slender [D. lyco- 

 podioides). 



17. Leaves acuminate, nerved | or to base of acumen : auricles 

 nearly reaching nerve, of more elongate rectangular cells (D. aqiiaticus 

 var. occidentalis) . Leaves subulate, nerve longer, ceasing in acumen 

 (except in D. asturicus) : a wide space between nerve and alar cells, 

 the latter shorter, less decurrent : nerve 40-70 i_i wide (18). 



18. Very robust and regularly pinnate : leaves large, with a long 

 subule, very regularly circinate, crowded (D. Wilsoni var. hamatns). 

 Less robust, more irregularly branched : leaves somewhat laxer, smaller, 

 more flcxuose and with a shorter subule {D. Wilsoni). 



19. Nerve very strong, 40 to 120 // wide (20). Nerve more slender 

 30 to 60 /.i wide : if wider, auricles reaching nerve (27). 



20. Leaves distant, spreading from a broad base gradually narrowed 

 into a widely acuminate plane recurved acumen : stems (20 cm. high) 

 plumosely pinnate : nerve reaching beyond middle 70-80 [i wide : basal 

 cells somewhat incrassate (D. asturicus). Leaves falcate to circinate- 

 secund, with a long chanelled subule, in which the nerve is more or less 

 engaged (21). 



21. Very slender, almost filiform : leaves from a short ovate tri- 

 angular base, suddenly narrowed to the reflexed subulate points : cells 

 shorter, basal about 3-4 times as long as broad : nerve up to 70 n wide 



{D. Sendineri var. gracilescens). More robust: leaf base longer and 

 acumen more prolonged : cells 8-24 times as long as broad {22). 



22. Leaves small, I-5-2-5 mm. long: rather densely tufted (2^). 

 Leaves longer, 2-5-4 rnm. long : more loosely caespitose (24). 



23. Much branched and rather rigid : leaves rather sudden acuminate- 

 subulate, strongly falcate to circinate {D. Sendtneri i. vulgaris). Softer, 

 branches short : leaves longly and gradually subulate, lightly appres.sed, 

 the points falcate-secund : although the leaves are as long as in the 

 preceding, the stems look slender and less turgid, owing to the straighter 

 more appressed leaves (D. Sendtneri f. tenuis). 



24. Very robust and stately (15-40 cm.) : branches long, often pinnate 

 and stem-like median cells very long, 70-120 /j, (25). Not so stout, 

 shorter, 10-20 cm. : median cells shorter, 50-80 fx (26). 



25. Leaves distant, slightly falcate, from an oval oblong base, 

 gradually narrowed to a long flexuose twisted subule : median cells 

 80-90 fi long: nerve 70-100 /< wide (I). Sendtneri var. trivialis). I^eaves 

 strongly falcate-secund, large, with very long setaceo-subulate points : 

 auricles very small, decurrent : nerve 90-120 ^t wide at base : cells 

 long and prosenchymatous to leaf base (median no u. long) : plant 

 dark green, almost black below (D. Sendtneri var. giganteiim). 



26. Auricles occupying ^ or less of the distance to the nerve {D. 

 Sendtneri). Auricles wider, occupying about \ the distance to the 

 nerve (D. Sendineri f. late-auriculata). 



■2-j . Median cells very long, 60-80 /< : alar cells occupying all or 

 nearly all the leaf base : nerve rather stout, 50-80 fi wide, reaching 

 above half way or entering base of acumen (28). Median cells shorter, 

 20-60 jj, : nerve weaker, shorter : alar cells occupying J to J of space 

 between margin and nerve (36). 



28. Basal sinus rather shallow and wide : leaves more or less falcate- 

 secund above, with a long usually canaliculate subule (29). Basal sinus 

 deep and narrow, almost orbicular through the points of the auricles 

 approaching {^2). 



29. Slender and gracile (10-15 cm.) : leaves small (up to 2-5 mm. 

 long), falcate, finely acuminate (30). Stouter, with broader leaves 

 and shorter leaf points (31). 



Naturalist 



