BULLETIN NO. 6T. 
The most important summer-flowering trees, the Lindens (Tilia) are 
beginning to bloom and the fragrant flowers of the different species 
will perfume the air during a large part of the month of July. In 
the collection are the three species of the northern United States,. 
Tilia americana , T. Michauxii, and T. heterophylla, all the European 
species, and several species from eastern Asia. Usually the trees of 
eastern Asia are more successful in this climate than those of the 
same genus from Europe, but to this general rule Tilia is an excep- 
tion. All the European species and their hybrids and varieties flourish 
in New England, but the Asiatic species are showing themselves bad 
growers here, and only the Japanese T. japonica and the north China 
T. mongolica have ever grown large enough in the Arboretum to flower 
and produce seeds. The latter is a small and apparently short-lived 
tree of only botanical interest. Tilia japonica is also a small tree 
here with drooping branches and light green foliage; it is one of the 
late-flowering species and is conspicuous in early spring as it unfolds 
its leaves a week or two before those of any of the other Lindens 
in the collection appear. 
The flowers of Tilia platyphyllos have been open for several days. 
This is the most widely distributed of European Lindens especially in 
the south, and it may be recognized by the yellow tinge of the leaves, 
by the thick covering of short hairs on their lower surface' and on the 
leaf-stalks, and by the prominent ribs of the fruit. It is not the hand- 
somest of the European Lindens, but it is the tree which is usually 
sold by American nurserymen as “the European Linden/' There are 
varieties with leaves larger than those of the type (var. grandifolia) y 
with erect branches forming a broad pyramidal head (var. pyramidata) 
and with variously divided leaves (vars. lanceolata and vitifolia). A 
handsomer tree, Tilia cordata , is the common Linden of northern 
Europe where it sometimes grows to a large size, the old historical 
Linden-trees of the north and central countries usually being of this 
species. This tree may be recognized by its small, thin, more or less 
heart-shaped leaves which are pale on the lower surface and furnished 
with conspicuous tufts of rusty brown hairs in the axils of the princi- 
pal veins. It has not been often planted in this part of the country, 
although it is specially valuable, for it is the latest of the Lindens to 
flower and supplies bees with food after the flowers of the other Lin- 
dens have faded. 
The handsomest, perhaps, of the Lindens of western Europe is by 
many students considered a natural hybrid between the two species 
already described, and is variously called Tilia vulgaris , T. europaea r 
T. intermedia and T. hybrida. Although widely distributed in Europe, 
this tree appears to be much less common than either of its supposed 
parents. It is a tall, round-headed tree, and large noble specimens 
can be found in the neighborhood of Boston where formerly it must 
have been more often planted than any of the other foreign Lindens. 
Two Lindens occur in eastern Europe, the Silver Linden, Tilia to- 
mentosa , and T. petiolaris. The former is a tree with erect-growing 
branches which form a broad, compact, round-topped, rather formal head, 
and erect leaves dark green above and silvery white below; this distinct- 
looking tree is not very common in eastern Massachusetts, but it can be 
often seen in the neighborhood of New York and Philadelphia. Tilia 
petiolaris is a more beautiful tree; this also has leaves which are silvery 
white on the lower surface, but drooping on long slender stalks they 
