169* 



ARBORETUM AND PRUTICETUM. 



PART III, 



ifclefcd by many botanists as a species, and 

 distinct enough in appearance, we have no 

 hesitation whatever in pronouncing it to be 

 merely a variety. 



V B, a. 4 pontira ; B. pontiea Lodd. Cat., ed. 1836; 

 and GtttJSg. 1549.; lias the leaves somewhat 

 larger than the species, and appears of more 

 robust growth. There is a tree of this kind in 

 the Oxford Botanic Garden, which, 40 years 

 planted, is 4j ft. high ; the diameter of the 

 trunk 1 ft. 1 1 in., and of the head 30 ft. At 

 Groome there is a tree, which, 40 years 

 planted, is 70ft, high; and in the Glasnevin 

 Botanic (Tardea, one 35 years old, which is 

 38 ft. high. The plants in Messrs. Loddiges's 

 collection are quite young, and not above 

 3 ft. or 4 ft. in height. 



S B. a. 5 urticifo/ia, B. wrticifoHa Lodd. Cat., has 

 the leaves deeply laciniated, serrated, and hairy. 



, 416., is described by the younger Linnaeus, as having its leaves 

 segments toothed ; " cut like those of hemp," according to 



\ B. a. 6 dalccarlica L. Supp. 



almost palmate, with th< 



Rose. 



*jf B. a. 7 macrocdrpa Willd. has the female catkins twice as long as those of the species. 

 Y B- o. S/uliis variegatis Dumont has the leaves blotched with yellowish;white. 



Other Varieties. B. £>opulifolia and B. daurica, given below as species, 

 are, we think, as much varieties as the preceding sorts; for, though 2?. juopu- 

 lifolia will come tolerably true from seed, yet it is often produced from seeds 

 of the common birch. B. daurica appears to be a variety of B. alba, stunted 

 from the climate in which it grows; and the same observation will apply 

 to B. sibirica, and some others, enumerated in the Catalogue of Messrs. 

 Loddiges for 1836. B. excelsa and B. nigra of some of the London gar- 

 dens are mere varieties of the common birch, and quite distinct from the 

 species described by botanists under these names, which are natives of 

 America. (See Gard. Mag., vol. xi. p. 502. 689.) There are some other 

 sorts in the collection at Messrs. Loddiges's ; such as B. undulata, B. 

 Thomnidna and B. Fischen'i, which appear to us to belong to B. alba ; but, 

 the plants being exceedingly small, we are not able to determine this with 

 certainty. B. laciniata being merely a cut-leaved variety of JS» juopulifolia, we 

 have included it under that head; as we have the sort named B. pendula, 

 in the collection of the Messrs. Loddiges. We prefer, in this case, as in 

 similar ones, giving varieties which have been generally considered species 

 as such, merely indicating our opinion by a letter in parentheses, for the 

 sake of disposing of the synonymes. There are some varieties of a trifling 

 nature given by Linnaeus in his Flora Succica : such as one with a rounder 

 leaf than the species, and pendent branches; one with a white, broad, and 

 acuminate leaf; one with brittle branches, and a blackish woolly leaf ; one 

 ( B. i\;itilis torminalis) with an oblong leaf; and, lastly, the dwarf birch, 

 probably the B. pumila of Lodd. Cat. These varieties are recorded in 

 Martyns MUler ; but, unless we are right in conjecturing B. pumila to be 

 the- last, we have not seen any of them. Dr. Agardh mentions "three 

 singular varieties with laciniated leaves ( li. hybrida Mamch) near Fahlun. 

 ( Gard. Mag,, w6L xh. p. 63.) The birch varies so much from seed, that 

 scarcely anj limits can be given to the number of sorts that might be 

 ■elected from B seed-bed. In extensive birch forests, also, whether in the 

 rocky scenery of Sweden, the bogs in the north of Russia, or on the hills of 

 Germany, fall-grown tree-, may be seen, as various in their foliage and habit 

 of growth as the young plants in seed-beds. For this reason, we arc in- 

 clined to think that there arc only two European species of birch, //. alba 

 and //. nana; and four American species, 11. papyracea, B. excelsa,//. 



Lenta, and B. nigra. 



