256 



GYMNOSPERMS 



others have five. Occasionally, there may be as many as eight leaves 

 on a spur. 



In Larix, Pscudolarix, and Cedrus, the number of leaves on a spur 

 is much larger, usually thirty to fifty, or even more; but the leaves 



are never so long as in Finns, seldom reach- 

 ing more than 25 to 40 mm. in length. 



The spur comes from the axil of a scale 

 leaf on the long shoot, and bears several 

 thin, membranaceous scale leaves, closely 

 wrapped around the spur, before it pro- 

 duces the needle leaves (fig. 262). The 

 needles are always lateral, the terminal 

 meristem persisting for a longer or shorter 

 time after the usual number of needles 

 has been formed. In Finns, where the 

 spur itself is deciduous, the growing point 

 produces only one set of needles, but in 

 forms like Larix, where only the needles 

 arc deciduous, the apical meristem pro- 

 duces many sets of needles, and, as in 

 Ginkgo, may grow out into a long shoot. 

 Sometimes, even in Finns, the apical meri- 

 stem, after producing the two-, three-, or 

 five-needle leaves, again becomes active, 

 and the spur proliferates, a long shoot 

 growing from the tip of the spur. Prolifera- 

 tion can sometimes be caused artificially. 

 If parts beyond the spur be removed, nu- 

 trition which would have gone to the re- 

 moved parts then goes to the spurs, and, 

 if the terminal meristem of the spur has 

 not died, proliferation is likely to occur. 



Besides the needle leaves and broader 

 leaves, many conifers have small, flat, 

 appressed leaves, as in Thuja, Lihocedrus, some species of Junip- 

 criis, and others (fig. 263). Another modification is seen in the 

 Japanese Sciadopitys vcrticillata, in which two long-needle leaves, 



Fig. 260. — Larix laricina: 

 tip of branch showing first 

 year's growth with leaves 

 borne directly on the^ long 

 shoot; and, below, three spur 

 shoots with numerous leaves; 

 natural size. 



