582 TRANSACTIONS OF SECTION K. 



knowledge of the- humus-content the water-content was meaningless, and the 



analyses widely discordant. But the ratio 57 " ' - reduces them to order. 



Hum us- Content 



This is most evident in dealing with successive layers of the same section, 

 e.g., a peat containing 170 per cent, of water lies immediately above a sandy sub- 

 peat with only 30 per cent., and the fine rootlets of bilberry penetrate both. 

 But the ratio is practically the same for each, viz., 3-0 and 2 9. So, again, the 

 ratio will reveal superficial drying by its low value when the actual water- 

 content may be very high. 



The ratio =-p is also a convenient way of expressing the humus-content 



of the peat. 



Conclusions. 



1. The Pennine peats form an homologous series, each homologue being suffi- 

 ciently distinguished by its water- and humus-contents to separate it from other 

 members of the series. 



2. These homologues correspond to the following recognised plant-associa- 

 tions : — 



I. Pure Eriophorum Moor on deep peat (19 analyses). — Characters : Peat very 



pure and uniform; water, 300-600 per cent. ; humus, above 80 per cent. ; 

 ash, purely vegetable, very low, under 2 per cent. ; water coefficient, 6"0. 



II. Rocky Edge of Eriophorum Moor (4 analyses). — Yaccinium Myrtiuus or 



Empetrum dominant. Characters: Peat still very pure, not so deep; 

 water, 250-300 per cent. ; humus and ash, as before ; water coefficient, 3 0. 



III. Transitional Eriophorum Moor (13 analyses). — A mixed association of 

 Eriophorum, Vaccinium Myrtillu*, Pteris, Calluna, Molinia, &c. Cha- 

 racters, peat moderately deep, still pure, but not so uniform and compara- 

 tively dry; water, 100-200 per cent, (average 160 per cent.); humus, 

 50-80 per cent, (average 64 per cent.) ; mineral residue now containing 

 rock debris, 10-40 per cent. ; water coefficient, 20. 



IV. Calluna Moor (28 analyses). — Characters, pei't shallow, impure. Two 

 types may be distinguished : (a) wet, with Erica tetralix present; water, 

 60-100 per cent, (average 00 per cent.); humus, 20-50 per cent.; water 

 coefficient, above 2 - 5 (average 3-3) ; (ft) typical, water, average 85 per 

 cent. ; water coefficient, 2 - 0-2'8 (average 2'3). The coarse sandy sub- 

 peat, with quartz grains, contains an average of only 25 per cent, water, 

 but water coefficient remains between 2'5 and 3'5. 



V. Molinia Moor (9 analyses). — This presents the only contradiction of cur- 



rent views both as regards water- and humus-contents, for the peat is 

 quite as pure as that of the Calluna moor, but distinctly drier. Cha- 

 racters, deeper than Calluna peat, but never pure. Water, 30-80 per cent., 

 average 56 per cent. ; humus, about 30 per cent. ; water coefficient, under 

 2 (average 1-93). 



3. The series constitutes an edaphic formation. 

 Note. — The consideration of Ui.atli Pasture is omitted. 



2. The Willing of Moorland Plants. By W. B. Chump, M.A. 



The purpose of the investigation, carried out in the summer of last year, is 

 to arrive at the physiological water-content of moorland soils. This is done 

 by determining the water still remaining in the soil when wilting definitely sets 

 in. A preliminary set of experiments made in 1900 had already given fairly 

 satisfactory results and a knowledge of the main difficulties and precautions ; 

 but they were neither numerous enough nor started sufficiently early in the 

 season to justify publication. The initial difficulty in the case of moorland 

 plants is to decide when wilting occurs. The indications common in mesophytes, 

 such as flaccidity, drooping or total collapse, are absent ; withering creeps on 

 so gradually that one is at a loss to decide where to draw the line. Experience, 

 gained by the sacrifice of some of the plants, furnishes a clue in some cases ; 

 and in several species, notably Molinia and Eriophorum angusli folium, a more 

 precise test was found in the rolling or folding of the leaves. 



