(31) 
Usually there are three points forming a triangle, or more and then forming 
either a curved line (Asimina), a horseshoe-shaped line ( Cephalanthus ), 
or a closed chain following the outline of the scar (Moms, Sambucus , Frax- 
inus), or separating in groups (Juglans, Cary a, Gymnocladus). The marks 
are somewhat concave (Aesculus) or convex ( Lindera ). 
THE TWIGS. 
The direction of the twig commonly agrees with the direction of the 
bud. The Sassafras has a peculiar growth ; the secondary shoots of the 
summer from the lower buds attain a greater length than the primary ones, 
and as the shoots are curved upward, the whole has the appearance of a 
chandelier ^Pl. Ill, Fig 7). The shoots are either smooth ( Fraxinus 
americana and sambucifolia , Acer , Crataegus ), or pubescent ( Fagus , 
Betula ), or rough hairy ( Corylus , Ulrnus fulva ), or tomentose-pubescent 
(Fraxinus pubescent, Cary a olivaeformis , Diospyros ), or prickly, and then the 
prickles are placed irregularly on the bark (Rosa, Rubus, Smilax ), or there 
is only one on each side of the scar, representing a stipule (Robinia, Zan- 
thoxylon). Prickles should not be confounded with spines (or thorns). 
Ribes has a spine below the persistent base of the leaf-stalk, and this rep- 
resents a bract. 
In many species we see ridges running downward from the leaf-scars 
(Populus monilifera, Rhus toxicodendron ) , in some species with opposite 
leaves these ridges are very sharp and prominent, and the twig becomes 
quadrangular (Fraxinus quadrangulata, Euonymus atropurpureus). 
The color of the twig is mostly brown, but other colors occur, 
red (Cornus sericea ), purplish (Cornus alternifolia, Asimina ) yellowish 
(Platanus), green (Sassafras, Euonymus, St a phyla, Negundo ), grayish 
[Fraxinus sambucifolia, Rhamnus), white, thickly covered with a white 
woolly pubescence (Salix Candida). 
THE PITH. 
The pith in a horizontal section of a twig shows different forms in the 
different species, and in the same individual. In the middle of the meri- 
thall (space between two single leaves or pairs of leaves or whorls), it is 
more or less circular in the majority of our species ; but sometimes it shows 
a hexagonal shape in species with opposite leaves ; in those with five leaves 
in two circuits, a pentagon ( Sassafras , Liquulambar), or a five-rayed star 
(Quercus, Fopulus). Near the upper end of the merithall (wrongly called 
“joint,”) the form of the pith is modified by projections towards the leaf 
or pair of leaves. 
The vertical section in Juglans and Celtis shows the pith in horizontal 
plates. I have observed this only in one other plant of our flora, the Phy- 
tolacca,. 
The color of the pith is mostly whitish, pure white in Sassafras, often 
with a rosy tinge in Tilia (cream color when older ), yellowish in Rhus glabra 
and Rhus toxicodendron, reddish in Gymnocladus, Cornus, Rhus aromatica , 
greenish in Gleditschia, brownish in Juglans cinerea , Carya amara. 
