82 Mr Willis and Mr Burkill, Ohsei-vations on [May 15, 



(4) Observations on the Flora of the Pollard Willows near 

 Cambridge. By J. C. Willis, M.A., Frank Smart Student of Gon- 

 ville and Caius College, and I. H. BuRKlLL, B.A., Gonville and 

 Caius College, Assistant Curator of the Herbarium. 



The observations contained in the following paper were begun 

 in 1890 and completed during the present year, and the results 

 obtained seem worthy of publication, as of some interest in them- 

 selves, and as confirming and extending those given by Loew in a 

 recent paper*. 



The trees examined are mostly on or near the banks of the 

 Cam and Ouse, from Ely on the north to Dernford on the south, a 

 distance of about 22 miles. They are polled at a height of 8 feet, 

 and stand in rows a few yards apart. Their tops contain large 

 masses of humus, in which occur many plants. 



Prof. Babinguon, in his Flora of Cambridgeshire, gives 950 

 species of plants as occurring in the County. Of these 350 may 

 be excluded, as water or bog plants or for other reasons, and of the 

 remaining 600 which could possibly be found, 80 species have 

 been observed in the willows. About 4000 trees were examined, 

 and a total number of 3951 records made. Where several plants 

 of the same species occur in one tree, they are counted as one. The 

 tables accompanying this paper show the actual number of records 

 of each plant for each section of the district examined, and also the 

 percentages and totals. 



The names given for the plants are those of the " London Cata- 

 logue of British Plants," 8th edition. 



The districts .studied are named A, B, C... and require a more 

 detailed description. 



A. This includes the trees found upon Coe Fen, within the 

 town of Cambridge, and in Grautchester, Shelford and Barraway 

 villages. All these regions are well wooded, and are near to 

 numerous gardens. The effect is seen in the figures : the most of 

 the records of Acer, Viburnum, Uimus, occur in this section ; Rosa 

 and GraiaegiLS, hedge plants, are below the average ; Sambucus 

 and Fraxinus stand high, and also Ribes, on account of the near- 

 ness of the gardens. 



B. Trees along the Cam, for about half a mile up stream from 

 Clayhythe bridge. Along the opposite bank runs a wood of ash 

 trees, &c., with a dense undergrowth of Anthriscus, Urtica, Galium, 

 Epilobium, &c. These plants appear in large number in the list. 

 Near the bridge are gardens, accounting for the presence of 

 Ribes. 



* "-Anfange epiphytischer Lebensweise bei Gefasspflanzen Norddeutschlands," 

 Verhandl. d. hot. Vereins der Prov. Brandenburg, xxxiii.. 1892, p. 63. Abstr. in 

 Bot. Gentralblatt, voL 52, p. 27. 



