1914] THOMSON—SPUR SHOOT 371 
after the first season, with the adult geminate leaves.’’ Lioyp’s 
(18) attention was attracted to the great persistence of the primary 
leaves of a young plant growing in the New York Botanic Gardens. 
In P. canariensis the leaves persist even longer than in P. Pinea. 
In P. rigida they are also very persistent. In the seedlings of most 
forms, however, the primordial leaves do not last beyond the 
second or third year. 
Primordial leaves are not, however, restricted to the seedling. 
According to Masters (19, p. 258), ‘they occur frequently on the 
lower part of the shoots of the year, as in Pinus sabiniana, Pinea, 
silvestris (sometimes), and other species’; also “in some cases, 
on the branches or stalks immediately supporting the cones, as 
in Pinus excelsa, etc.” In P. monophylla, Etwes and HENRY 
(7, p. 1056) have noted that “in cultivation adventitious shoots 
bearing flattened primordial leaves are occasionally produced on 
the lower branches.” SHAw (25, p. 206), in speaking of the “‘sum- 
mer”’ growth of certain southern pines of the United States, says: 
“this growth, in the summer, differs from the spring growth not 
only in its less development, but also in its green bracts, which, 
not being required for the protection of the winter bud, assume 
more or less completely the size, color, and character of the primary 
leaf.” Sarcent (24, p. 4) states that: “Pinus rigida and Pinus 
echinata are the species of the United States which generally bear 
primary leaves on branches, or produce freely shoots from the 
stumps of cut trees. These shoots, which are clothed with primary 
leaves, grow vigorously for a few years, and then usually perish.” 
ENGELMANN (8, p. 163) speaks of this feature in P. inops, P. rigida, 
and P. canariensis. In the last mentioned, it is very prominent 
in some instances. Miss Coorey (4) refers to and figures a tree 
at Naples which was practically clothed with shoots bearing 
Primary leaves. A young specimen of the same species in the 
New York Botanic Garden shows many reversions to primary 
foliage. Whether in these instances all the reversions may not be 
the result of injury is uncertain. Wounding does give a response 
in the case of the production of resin canals for several years after 
the injury, especially prominent being the response in young twigs 
which are formed subsequently to the wound, and it is probable 
