348 Yorkshire Naturalists at York. 



prevented the accumulation of rich fen peat, and coupled with the in- 

 efficient drainage, have led rather to the formation of a thin acid peat 

 layer, and the ultimate development of the damp heath type of vegetation 

 in which Calhtna, Erica Tetralix and Molinia cosrulea are locally dominant, 

 apparently depending largely on the depth of the imderlying sand. 

 Depressions in the underlying clay, Avhcrc sand is often absent, are filled 

 with pools, round which /uncus effusus, Carcx data, Eriophortim angusti- 

 JoliuDi or Hvpericum elodes may be abundant. 



The rabbit warren at Tillmire offers an extreme example of the 

 conditions found at Skipwith. Here, however, another factor, 'rabbit 

 pressure,' has also to be considered. The vegetation is chiefly 'grass 

 heath' dominated by Agrosiis vulgaris, with which Deschampsia flexuosa, 

 Agrostis alba, Triodia decmubens, and Festuca ovina are also frequent. 

 There can be little doubt that here the development of Calluna heath 

 is prevented by the grazing of rabbits and the manurial effects they pro- 

 duce. Similar effects have been described in detail by Farrow in Breck- 

 land [Journ. Ecol. IV., p. 57). Since, however, it is the depth of the 

 sand which leads to its suitability for rabbits, the vegetation type found 

 here must ultimately depend, to a certain extent, upon the glacial 

 phenomena previously mentioned. 



The presence of such plants as Riccia fluitans, Ricciocarpus nutans, 

 Lenina minor, L. trisulca, Hydrocharis Morsus-Ranae and Hottonia 

 palusttis in the ditches and pools at Askham Bog is probably important, 

 since these plants are characteristic of a plant community only found in 

 waters at least moderately rich in lime and usuall}^ containing nitrates. 



Botany (W. H. Pearsall).^ — The botanical members present were 

 handicapped by the dryness of the summer, Tillmire and Skipwith 

 commons being unusually dry. At Tillmire, few species of interest 

 were noted e.xcept Conium maculatum, Apiinn inundatum, A. nodiflorum 

 and Samolus Valerandi. 



Askham Bog was more fruitful, though the Carices were long past their 

 best. Mr. F. E. Milsom gathered Chiloscyphus polyanthus, LopJiocolea 

 cuspidata, Riccia fluitans and Ricciocarpus nutans, the two latter liver- 

 worts being strilingly abundant. No noteworthy mosses w-ere observed, 

 but Sphagnum cymbifolium Ehrh. and S. acutijolium Ehrh. were frequent, 

 and Aulaconniiuni andyogynuni was also present. 



Of the higlier plants, besides those previously mentioned, the following 

 are worthv of record : — 



Spargunium neglectum Rubus Caesius 



Scirpus setaceus Vicia sylvatica 



Juncus obtusiflorus Thulictrum flavum 



Carex ripuria Dryopteris Thelypteris 



C. ucutiformis v. spadicea Roth. Carex elata 

 C. Goodcnomii v. juncea Fr. C. julva 



and v. chlorostachya Druce C. flava 



C. G^-deri v. elutior .\bd. 

 IVIr. T. Cryer also ob.served Pot. colorutus on the dry peat of the skating 

 pool. 



One of the most striking features of Skipwith Common was the 

 remarkable abundance of Hypericum elodes along the margins of the 

 pools, due no doubt to the dryness of the summer. 



Gentiuna Pneumonanthe, Utriculuria vulgaris, Hydrocharis and Carex 

 pulicaris were also observed, and along the rix'cr banks Allium Scorodo- 

 prusum and Euphrasia nemorosa. 



Fungi : Basidiomycetes (A. E. Peck). — The long-continued drought 

 had brought about conditions quite unsuitable for the growth of fungi. 



Lentinus Icpideus grew at the foot of a wood fence in Heslington 

 village. Keslington Common gave no records. 



Askham Bog, being much dried up, was probably in better condition 



