Trachelium is another genus of Campanulacese, which is very distinct in feature from any of the other genera. The only species, T. caeruleum, which has proved hardy in this country is a native of southern Italy. It grows about 1 1/2 foot high, with many erect stems clothed with ovate acute dark olive-green leaves, and terminating in crowded corymbs of dark azure-blue funnel-shaped flowers, lasting from June till August. It is rather a showy plant while in flower, but the flowering period is followed by one of considerable seediness. Its chief recommendation is, that it adapts itself pretty comfortably to droughty situations, and is quite at home with a handful or two of soil on an old wall or piece of rock.

In the natural order Ericaceae there are very few hardy herbaceous plants. Among the Chimaphilas, Pyrolas, and Monotropas, there are some curious and pretty things; but in a horticultural sense they are almost destitute of beauty, and at the most can only be recommended here for cultivation among alpines in partially-shaded rockwork, in sandy peat and a little loam. They should never be disturbed while doing well. But there are certain of the shrubby genera of this order of plants which contain species and varieties of great excellence for the herbaceous border, the margins of shrubberies, for grouping in the spring garden, and for decorating rockwork, as taste and circumstances may prescribe. Erica yields the largest number of valuable things for these purposes. E. carnea and its varieties form, perhaps, the most interesting and beautiful group of these hardy heaths. They begin to bloom often so early as January, and continue flowering on till May and June. They are most easily cultivated, and, being of dwarf compact habit, they are available for the spring garden; and if kept in pots in the reserve ground, their value as temporary tenants of the beds of the summer flower-garden, in circumstances requiring these to be filled in winter, is very high indeed.

E. tetralix, and the few varieties sprung from it, are handsome, and flower from June till August and September. E. Australis is another early blooming species. It comes on in March, and lasts till the end of May, and often into June. E. Mediterranea begins to flower about the same time as the last-named species, but continues for a shorter period. This is by some considered merely a more erect and taller form of E. carnea, but as it is a remarkably distinct form, it is quite entitled to a specific appellation in gardens at least. The var. nana alba of this species is a fine compact sort for rockwork or for the spring garden. E. cinerea, one of the most common of our Scotch heaths, is at the same time, in some of its varieties, one of the most handsome. They flower throughout the summer and autumn. E. vagans and its varieties, also summer-flowering, are pretty dwarf dressy things. E. ciliaris is one of the handsomest of hardy heaths, with large purple or pink flowers in leafy racemes. It flowers in summer and autumn. Some of the varieties of the common "Ling" Erica or Calluna vulgaris, are pretty, and well worth a little attention.

They are now rather numerous, and vary much in habit, some forming neat tufts or cushions, while others are rather loose and straggling.