1893.] distributed by the Cambridge dust-carts. 95 



other plants but few rise in number n( individuals above fifty ; 

 while the common Dandelion (Taraxacum officinale) is reduced 

 to ten roots. In species, Oramineae and Gompositae are the best 

 represented, each containing more than one-sixth of the total. 

 Leguminosae, Gruciferae, and Polygonaceae are fairly numerous. 

 These five orders make up three-fifths of the whole; the other 

 two-fifths consisting of representatives of no less than 22 orders, 

 including Garyophyllaceae, Rosaceae, Umhelliferae, Scrophnktrineae, 

 and Labiatae, all numerically important in the British Flora. 

 Gyperaceae is not represented, nor is Ewphorbiaceae : the latter 

 we should certainly expect as the soil is rich, so rich that the 

 grasses, essentially a manure-loving order, are very luxuriant, and 

 there is not that keen struggle for existence which is fatal to our 

 common British Euphorbiae^. 



Of published floras the only one which is similar is Vallot's 

 little list of 45 species from the Place du Carroussel in his Floi'e 

 du Pave de Farts. These plants are distributed through the 

 orders in a manner similar to those with which we are dealing ; 

 and we find the same forage element — an element which forms a 

 very considerable percentage of the naturalised plants of any 

 country in the world. 



We know how European hay sold at an Australian port has 

 introduced European plants ; how Trifoliwm repens has taken 

 possession of the Pampas near Buenos Ayres ; how the German 

 army in 1871 established two clovers in the neighbourhood of 

 Paris •{*, the seeds falling out of the hay which they carried for 

 their horses; and so here we see the same kinds of plants carried 

 through small distances in our own country and our own town. 



Monday, May 29, 1893. 

 Dr E. W. Hobson, Secretary, in the Chair. 



The following Communications were made to the Society ; 



(1) On the Kinematics of a Plane, and in particidar on Three- 

 bar Motion; and on a Gurve-tracing Mechanism, tenth exhibition 

 of apparatus. By Prof Cayley. 



[To be published in the Transactions.] 



(2) On Gontour Integration. By H, F. Baker, M.A., St John's 

 College. 



(3) Electric stability in crystalline media. By J. Larmor, 

 M.A., St John's College. 



* The seeds oi Euphorbia Peplus (-00041 gramme) weigh less than White Clover 

 TrifoUum repens (-00059 gramme), and this plant and others of the same order 

 have been found in various comparable situations. Cf. Vallot, Flore du Pave de 

 Paris et des Ruines du Conseil d'Etat. Deakin, The Flora of the Colossexim of Rome. 

 Richard, Florule des Clochers et des Toitures des Eglises de Poitiers. 



t Vallot, Floiule du Pantheon, Journal de Botanique, vol. i. 1887. 



