566 TRANSACTIONS OF SECTION K. 



favour transpiration or hinder absorption. The author has confirmed these 

 results in the case of Spircea Ulmaria, and traced the history of the develop- 

 ment of both kinds of cells in detail. The relation of the hairs and palisade 

 cells to external factors has also been followed at each stage of development. 



The conclusion arrived at is that the initial stimulus leading to a marked 

 development of these special cells is to be sought in a diminished water-supply 

 in the cells themselves. On the other hand, a considerable degree of turgor is 

 necessary for the actual stretching growth of the cells. In all probability these 

 apparently opposed conditions occur more or less regularly in Nature, in the 

 form of periodic fluctuations of turgor. Thus transpiration during the day- 

 time (especially when excessive) would afford the stimulus of diminished turgor ; 

 while the increasing turgor of the cells during the night-time would allow 

 of their actual growth. 



7. The Forest Stages represented in the Peat underlying the Moorlands of 

 Britain. By F. J. Lewis, D.Sc, F.L.S. 



8. Types of Vegetation in the District round Macclesfield. 

 By Miss Lilian Baker, M.Sc, and B. W. Baker, B.A. 



Introduction. — The area being studied comprises parts of Cheshire and Staf- 

 fordshire, the county boundary running across the south-east corner of the tract. 

 The four corners are approximately marked by the towns of Northwich, Crewe, 

 Leek, and Macclesfield. It includes part of two regions — namely, (1) the 

 Cheshire. Plain, occupying the western portion, largely cultivated, with numerous 

 parks and wooded estates, and a few sandy heaths and ' mosses ' ; and (2) the 

 Pennine Foothills, occupying the eastern portion. The latter consists of 

 approximately parallel ridges, intersected by the Dane Valley and other wooded 

 ravines, and covered by moors. The highest altitude, that of 1,500 feet, is 

 attained by the bleak moorland tract of Macclesfield Forest. 



The total rainfall may be said, generally, to increase from the level western 

 parts towards the hilly east. The plotting of monthly rainfall curves has shown 

 that there is considerable local variation from the curves for Great Britain. 



Geology. — The two regions of the sheet show marked differences in structure. 

 The Plain consists of Triassic rocks, buried in Pleistocene times under a thick 

 covering of glacial deposits — boulder-clays, sands, and gravels. The hill region 

 consists of Carboniferous rocks occurring in the following strata : (1) Coal 

 measures, (2) Millstone grit series, (3) Pendleside series, (4) Carboniferous lime- 

 stone. The shales of the Pendleside series, being most easily eroded, are found 

 to occupy river valleys, the other strata standing out in bold relief. The dis- 

 tinction between the hard grits and the softer crowstones influences the con- 

 tour of the land as well as the character of the soil. 



Peat mosses occur on the Plain in the position of former Glacial lakes, but 

 have been largely reclaimed. 



Vegetation.— Moorland and Heath Associations are represented by : — 



(1) Vaccinium Myrtillus, either pure or with more or less Calluna. Its 

 replacement by Empetrum nigrum presents interesting features, e.g., the 

 summit ridge of Congleton Edge, proceeding in a north-easterly direction, 

 shows the following succession : (a) Calluna vulgaris with V. Myrtillus, 

 Eriophorum angustifolium, Erica cinerea; (b) Vaccinium Myrtillus with 

 Calluna vulgaris; (c) Pteris aquilina with V. Myrtillus and C. vulgaris ; 

 (d) Pteris aquilina with V. Myrtillus and Empetrum nigrum; (e) Vac- 

 cinium Myrtillus with much Empetrum and little Calluna. 



(2) Eriophorum angustifolium, with or without Calluna, according to 

 the amount of moisture present. 



(3) Calluna vulgaris, with different accompanying plants, according as 

 it occurs on peat or on sandy soil. 



