i 9 2o] DUPLER—TAXUS CANADENSIS 495 



strobilus already described (13), having very thick epidermal walls, 

 especially on the outer surface, stomata on the inner surface, and 

 rather large air spaces. They are brownish and lack chlorophyll. 



During its first season the primary shoot is a dwarf branch of 

 limited growth, and the development of the secondary shoot 

 results in its tip becoming pushed aside (fig. 2) and remaining 

 dormant for a time. Externally this gives the appearance of a 

 single structure with a terminal ovule, a situation which may 

 explain some of the earlier views as to the position of the ovule. 

 Van Tieghem (37) apparently was the first to point out this 

 behavior of the primary axis. According to Schumann (31), and 

 also Pilger (23), the primary axis ends blindly, and the so-called 

 tip of the primary shoot is the knob of a reduced side shoot which 

 may at times grow out to form a second secondary shoot. When 

 this occurs the primary axis may form a short knob between the 

 two secondary shoots. This view does not agree with the facts and 

 has received but little support. 



Second season's growth. — The tip of the primary shoot 

 remains dormant until the next spring, when its growth is renewed, 

 resulting either in its continuation as a dwarf structure, as in the 

 first season, or in its growth as a leafy shoot, like that from the 

 ordinary vegetative bud, a fact first noted for T. baccata by Stras- 

 burger (35). This leafy shoot may bear only a few small leaves 

 (fig. 3) and develop no further during the second season, the sub- 

 sequent behavior of such small shoots not being known. It also 

 may develop as an ordinary leafy branch, differing in no way from 

 other leafy branches except in bearing the secondary shoot at 

 its base (figs. 4, 5), and, like any other vegetative branch, bearing 

 vegetative and reproductive buds of the next season. Occasionally 

 the primary axis remains dormant as a vegetative bud for a season 

 or more. In such cases the reproductive nature of the first season 

 can be told only by the scars of the old secondary shoot (fig. 6). 

 Normally, however, the primary shoot continues its dwarf and 

 reproductive character for the second and later seasons, producing 

 a few scales as in the preceding season, with one or two new sec- 

 ondary shoots on the new growth. It has been generally assumed 

 that the primary shoot produces fruiting structures for only one 



