TREES OF THE CAMBRIDGE BOTANIC GARDEN. 



15 



the last three years has not increased in height, but during this time it 

 has increased from 27 to 36J ft. in diameter. 



38. Fendlera rupicola Engelmann. 



I am tempted to have a note on this plant because apparently 

 it is regarded as doing well only on the Continent. Here it does 

 perfectly and is most beautiful, producing wreaths of white flowers 

 nearly, if not quite, ij in. in diameter. It is growing on the south 

 side of the Cactus-house and is over 7 ft. high ; its recorded height, 

 presumably wild, being from 3 to 6 ft. Its habit is upright, but its 

 width is nearly 4 ft. No doubt it is one of the best of subjects for a 

 hot sunny position, where it does succeed. It is one of the shrubby 

 Saxifragaceae, most resembling Philadelphus , and is a native of the 

 South-Western United States. 



39. Populus serotina Hartig. Black Italian Poplar. 



This is the commonest Poplar in the British Isles and one of the 

 two tallest trees, the other being Ulmus campestris, the English 

 Elm. It is a hybrid between the American P. deltoides and the 

 European P. nigra. It is always a staminate tree, and is propagated 

 by cuttings. One of the most interesting trees in the collection is 

 the true P. deltoides, one of its parents. P. canadensis, believed to 

 originate from the same cross, is always female. 



40. Populus nigra var. viridis Lindley (Syn. 238 (1829) ; Camb. 

 Brit. Flora, ii. p. 10). 



This is an extremely interesting tree found in Jersey, Suffolk, 

 Norfolk, and Cambridgeshire. The leaves are broader at the base 

 than are other varieties, and the green is of deeper hue. 



41. Populus italica Moench. 



This is the well-known Lombardy Poplar, usually referred as a 

 variety to P. nigra. Some authorities dissent from this determination, 

 and Dr. Moss considers that differences are infinite in number. Only 

 the pistillate tree is cultivated. It is regarded as possibly a native of 

 Eastern Europe or North-West Asia, and travellers may be asked 

 to observe on the question. Ascherson and Graebner believe it to 

 be native of Eastern Europe. From the habit of the tree I should 

 expect that it is nowhere wild, but I quite agree that it is a fastigiate 

 form of something that is not common P. nigra. 



Group III. — Elms, in the Botanic Garden and Outside. 



Elms flourish in Cambridge and may be regarded as the tree of 

 the district. All those to which I require to draw attention belong 

 to the British series. They are classified as follows by Dr. Moss in 

 the new Cambridge British Flora. This table is a valuable one and I 

 give it complete, but there appears to be no very fine example in 

 Cambridge of the third series, which consists of one species, Ulmus 

 glabra, the Wych Elm. 



