Dec., 1902.] 
Observations on Self-Pruning. 
3 2 9 
Euonymus atropurpureus Jacq. Shed twigs from one to four years old 
■were collected. 
Acer saccharinum L. 
Acer rubrum L. 
Polycodiutn stameneum ( L.) Greene. Self -prunes twigs abundantly. 
Vaccinium vacillans Kalm. 
The following two grapes were studied and found to prune in 
the normal way for such plants by the formation of cleavage 
planes corresponding to leaf nodes in twigs of the season : 
Vitis labrusca L- Wild variety.! 
Vitis bicolor Le C. 
As stated in the beginning of this paper cleavage planes are 
often formed to separate the fruit from the parent plant. It is 
interesting to note some of the ways in which this is accom- 
plished. In the simplest cases a cleavage plane is formed at the 
basae of the fruit, which falls off while the peduncle dries and 
decays away. This is the case in Rhus glabra L. In others the 
separation layer is formed at or near the base of the peduncle, as 
for example in the ground cherry, Physalis pruinosa L. In this 
herb a very perfect cleavage plane is formed in the peduncle. In 
the apple and pear the separation of the fruit from the tree is 
accomplished in the same way by the development of a rather 
imperfect cleavage plane or separation layer. In some plants, as 
in Prunus americana Marsh., or in Benzoin benzoin (L.) Coult., 
the fruit first falls off and afterwards a cleavage plane is formed 
at the base of the peduncle. In the plum the peduncle sometimes 
dries off and is not immediately shed, even though the separation 
layer is formed. When the fruit is produced on panicles or 
cymes there are also several methods of procedure. In the dog- 
woods, as in Cornus asperifolia Mx., the berries drop off singly, 
and later the fruiting cyme is closely excised by a smooth cleav- 
age plane ; while in the smooth sumac, as stated before, the 
berries drop off in the same way, but the much branched panicle 
remains to decay gradually. In the chestnut (Castanea dentata 
(Marsh.) Borkli.), the stems which bear the burs become quite 
woody, but a cleavage plane is formed and the entire fruiting 
branch is thus pruned off. 
The writer has had some difficulty in looking up the literature 
on the subject of self-pruning. This may be because no dis- 
tinctive term has come into use for this common and most 
interesting phenomenon of our shrubs and trees. The following 
is a list of recent American papers bearing upon this subject : 
18S5. Trei.EASE, Wm. When the Leaves Appear and Fall. Second 
Ann. Rept. Agr. Exp. Sta., Univ. of Wisconsin, for 1884. p. 59. 
1892. Foerste, Aug. F. On the Casting-off of the Tips of Branches 
of Certain Trees. Bull. Torr. Bot. Club. 19 : 267-269. 
