1920] DUPLER—TAXUS CANADENSIS 



50i 



unlimited growth, however, then havine both the 



tative and reproductive possibilities of any other branch. The 

 occasional behavior of the terminal bud in becoming a dwarf 

 primary shoot recalls a similar behavior in Ginkgo, although one 

 must not infer too much as to relationshiD on this account. 



Secondary shoot 



General features. — The primordium of the secondary shoot 

 first appears as a lateral structure in the axil of one of the upper- 

 most scales of the primary shoot (fig. 34), soon becoming conical 

 (%- 35)- It is generally stated that the terminal scale is the fertile 

 one, but one or more small scales usually appear above the fertile 

 one, as was pointed out in T. baccata by Van Tieghem (37). Dif- 

 ferent writers have assigned definite scales of the primary shoot 

 as the fertile one in T. baccata, Van Tieghem claiming the eleventh, 

 Strasburger (36) the eighth or thirteenth, and Pilger (23) the 

 seventh; but this varies and is of no special importance. Fre- 

 quently two of the scales are fertile and two secondary shoots occur, 

 the tip of the primary shoot then appearing between them (fig. 36). 

 In Torreya there are usually two secondary shoots on a primary 

 shoot, but Strasburger 's account that in rare cases in Torreya 

 the primary shoot behaves as a secondary shoot, and bears a third 

 ovule above the two secondary shoots, does not apply to Taxus. 



The rudiment of the secondary shoot develops rapidly, producing 

 the three pairs of decussate scales* in rapid succession, the cyclic 

 arrangement of which is in contrast with the spiral arrangement of 

 the scales of the primary shoot. The first pair stands transversely 

 to the fertile scale. Van Tieghem held that while the scales are 

 decussate there is an indication of a spiral tendency, a view 

 necessary to his theory that the ovule is an axillary structure of 

 the sixth scale of the secondary axis. Practically all investigators 

 agree as to the decussate nature of the scales, as there seems to be 

 no basis for regarding the scales as having a spiral arrangement. 

 The scales of the secondary shoot are considerably larger than 

 those of the primary shoot, and contain chlorophyll, the outer 

 epidermis being heavily cutinized, and stomata occurring on the 

 inner surface. In the early stages these scales protect the young 



