BULLETIN NO. 46. 
No other North American tree is so familiar to the people of so 
many different parts of the world as the False Acacia or Yellow Locust 
of the Appalachian Mountain forests, Robinia pseudacacia, and it is 
now naturalized in many regions far removed from its native home. 
No other exotic tree has been so generally planted in northern and 
central Europe since its introduction into the garden of the Paris 
Museum in 1636 by the King's gardener Robin, whose labors it com- 
memorates; and no other American tree has given rise to such a vol- 
uminous literature. The cheerful light green foliage and hanging 
clusters of fragrant white flowers are known to everyone who has ever 
looked at trees. The value of the timber which it produces, the rapid- 
ity of its growth, its power to adapt itself to different soils and to 
reproduce itself rapidly by seeds which germinate readily and by stump 
and root shoots, would make it a most valuable subject for forest and 
coppice planting in this country if it could be protected from insects, 
but the value of the Locust is practically destroyed in nearly all parts 
of the United States beyond the mountain forests which are its home 
by the borers which riddle the trunk and branches. Owing to the 
difficulty of keeping the Locust in a presentable condition here no 
serious effort has ever been made to bring together the interesting 
varieties or ‘‘sports" of this tree which have appeared from time to 
time in European gardens and are largely planted in European collec- 
tions of trees. At least thirty of these varieties are now known; the 
one most often seen in Germany, especially in suburban gardens, is 
the so-called Parasol Acacia (var. umbraculifera). The short branches 
of this plant form a compact spherical head which is usually grafted 
on a tall stem of the common Robinis, as in this country a dwarf form 
of the Catalpa is made into a “standard" by grafting it on a tall stem 
of the tree form. The only abnormal form of the Robinia thoroughly 
established in the Arboretum is one of the most remarkable of them 
all; var. monophylla, in which the leaves are reduced to a single broad 
leaflet. 
The two pink-flowered arborescent Robinias, R. viscosa and R. neo- 
mexicana, are also subject to attacks by the borer. R. viscosa , the 
Clammy Locust, is not yet in flower but its near relative, the Rocky 
Mountain species, R. neo-mexicana, is now covered with its short clus- 
ters of pale rose-colored flowers. More beautiful perhaps than either 
of these trees is a hybrid of the Rocky Mountain species with R. pseu- 
dacacia , R. Holdtii, named for the Colorado nurseryman in whose 
establishment it appeared a few years ago. This tree is very hardy; 
it appears to suffer less than its parents from borers, it grows rapidly 
and plants only a few feet high cover themselves with pale pink flow- 
ers. This tree, which is not yet often seen in eastern collections, is 
an interesting and valuable addition to the rather short list of trees 
which flower here in early summer. The Robinias are planted with 
the other trees of the Pea Family on the right-hand side of the Meadow 
Road beyond the piece of natural woods. 
The latest of the American Magnolias are now in flower, M. macro- 
phylla and M. glauca. The former is a medium-sized tree with wide- 
spreading branches and is distinguished by the fact that of all trees 
which grow beyond the tropics it has the largest leaves and the largest 
flowers. The leaves of this remarkable tree are silvery white on the 
lower surface, from twenty to thirty inches long and from eight to 
