258 



GYMNOSPERMS 



A. 



Fig. 262. — Pinus laricio: 

 spur shoot from the axil of a 

 bract (6), with scale leaves 

 and two needles and the grow- 

 ing point between them; X 1 2. 



Tule," in southern Mexico, is evergreen. 

 This tree is generally regarded as Taxo- 

 dium miicronatum, although some prefer 

 to call it T. distichum var. mucronaturn. 



In Pinus slrobus and P. paliistris the 

 leaves fall the second year, but in most 

 species they live longer: in P. sylvcstris, 

 3 years; Pinus cemhra, 4-7 years; and in 

 P. aristata and P. baljouriana they persist 

 for even 12-14 years. In Picea excelsa and 

 Abies alba the leaves live from 6 to 9 years 

 and, sometimes even 10-12 years. In some 

 of the Araucariaceae the leaves may not 

 fall until the branch which bears them 

 breaks off. 



The evergreen leaf and the beautiful 

 habit have made the conifers very popular 

 as decorative plants on lawns, in city parks, 

 and around farm houses in the country. 

 Unfortunately, the dirt, dust, smoke, and 

 perhaps gases of a large city are fatal to 

 plants with leaves which must function 

 more than one year. Thirty years ago, in 

 Washington Park, Chicago, Pinus laricio, 

 P. sylvcstris, Picea cngclmannii, Picea ex- 

 celsa, and various other conifers were 

 prominent decorative features; but, as the 

 city developed southward and Cottage 

 Grove Avenue lost the features which 

 gave it its name, the conifers died. South 

 of the city, a region of steel mills, stone- 

 crushing plants, and sulphuric acid facto- 

 ries, a region formerly covered with a 

 luxuriant growth of Pinus banksiana, the 

 pine keeps retreating several miles in ad- 

 vance of the progress of civilization. Plants 

 with leaves which must function more than 



