94 3Ir Burkill, Notes on the Plants [Ma,y 15, 



Mr Willis and I in studying the flora of the tops of Pollard 

 Willows near Cambridge* have found the importance of bird distri- 

 bution shewn in a very forcible manner. But from the street 

 sweepings we get a flora of an extremely different type; excluding 

 the fruits of the traffic element, we find only Solanum nigrum 

 and Crataegus Oxijacantha with fleshy fruits, and these not neces- 

 sarily distributed by birds, and of burred fruits only Galium 

 Aparine, Bidens tripartita, Arctium Lappa and Myosotis arvensis. 

 Of the other 82 plants some have wings or pappus, e.g. Cnicus, 

 Rumecc, and many grasses, but many are without special adaptations 

 for dispersion in their seeds. 



Kichard, in his Florule des Clochers et des Toitures des hglises 

 de Poitiers has shewn how the two churches Saint Pierre and 

 Sainte Rhadegonde, situated nearest to the sandy hills, possessed 

 when he investigated their flora about four times as many plants 

 as any of the five churches remote from these hills. Light seeds, 

 such as those blown across to the Poitiers churches, are by no 

 means absent from this street-sweepings flora. Seeds such as 

 would be carried easily in any one of those clouds of dust which 

 the wind may blow along our streets weigh but little. 

 Papiaver Rhoeas, •00011 gramme, 



Capsella biirsa-pastoris, '00015 gramme i*. 

 Of seeds distributed by man one seed of Rape (Brassica Napus, 

 '0038 gramme) weighs as much as 34 Poppy-seeds, and one seed 

 of Buckwheat {Fagopyrum escidentum, '0267 gramme); as much 

 as 178 Shepherd's-purse seeds. 



The Roadside element, which is principally made up of tliese 

 small-seeded plants, is largely swollen through the rural nature of 

 some of our roads, e.g. Queen's Road. It is this fact which causes 

 the Hay element and the roadside element to overlap to such an 

 extent; but the prevalence in the street-sweepings of the capsules 

 of Rkinantlms Grista-galli — a plant common enough in the hay- 

 fields on the clay land near the town, but not found in it, — and 

 the nature of the debris which accumulates in such places as 

 Tennis-court Road, are facts which in themselves testify strongly 

 to the importance of seed distribution by means of hay, much of 

 which cab-horses scatter in feeding. In fact oats, which are 

 given to such a great extent to these hordes, always may be 

 seen lying scattered about cab-stands. 



In composition the flora is peculiar; Poa aniiva is the dominant 

 species, and next come Poa trivialis and Daciylis glomerata. Of 



* Observations on the flora of the Pollard Willows near Cambridge. Proc. 

 Cam. Phil. Soc. viii. 1893, p. 82. 



t We may compare the seeds of the Epiphytic Phanerogams where the need of 

 effectual distribution is more pressing. Dendrobium attenuatum Lindl. "00000565 gr. 

 AeschynantLus -00002 gr. Goebel, Pfianzenhiologisclie Schilderuvgen, vol. i., 

 'Epiphyten.' 



