CONIFER ALES (PINACEAE) 235 



of the Taxodineae, as witnessed by Sciailopitys, Sequoia, and Cryp- 

 tomeria (141); they are generally present (one or two) in the cotyle- 

 dons of Abietineae; and there are several in the cotyledons of the 

 Araucarineae (154). 



Even tyloses have been used in the recent intensive study of the 

 vascular anatomy of this group. Chrysler (140) has found that 

 they are restricted to Pinus, in which they occur in the heart of the 

 root and in the first year's growth of the axis of the ovulate strobilus. 

 This restriction was demonstrated by an investigation of the root 

 wood of thirty-two species representing thirteen genera, and of the 

 cone axis of twenty-three species representing eight genera. He finds 

 that, although they occur only in Pinus, they may be induced by 

 wounding, and raises the question whether they may be a feature 

 of phylogenetic importance as are the resin canals. 



The latest anatomical character applied to the comparative study 

 of the vascular anatomy is obtained from the "bars of Sanio," which 

 are cellulose thickenings in the walls of tracheids and appear as hori- 

 zontal or more or less semicircular markings, which stand out clearly 

 with proper staining. Miss Gerry (168) has investigated their oc- 

 currence and character among the Coniferales, finding them in 

 thirty-five of the living genera, but lacking in the living and mesozoic 

 araucarians. This emphasizes the distinctness of the araucarians from 

 all the other Coniferales. 



THE LEAF 



The distribution of foliage leaves and scales is far from uniform 

 among the Pinaceae. There may be foliage leaves only, as in Arau- 

 carineae and most Cupressineae; and in case there are both foliage 

 leaves and scales, the two may occur on the same shoot, as in Abies, 

 or on different shoots, as in Pinus. 



The foliage leaves of Pinaceae are quite variable in form, from small 

 discoid ones closely imbricated and appressed upon the axis ("con- 

 crescent"), as in many of the Cupressineae, to the characteristic free 

 needles of the Abietineae, and the broad blades of some of the Arau- 

 carineae (Agathis) (figs. 256, 258). In general, the phyllotaxy is 

 spiral, but in the Cupressineae it is cyclic. The foliage leaves are 

 very persistent, functioning one to ten years, the basal growth permit- 



