CONIFERALES 



borne on a spur shoot, are united by their 

 edges throughout their entire length. In 

 Phyllodadus, the spur shoot, coming 

 from the axil of a bract, becomes flat- 

 tened into a leaflike branch — phylloclad 

 — ^which functions as a leaf (fig. 264). 



In the seedlings, of all these cases with 

 modified leaves, the first leaves are of the 

 familiar needle type (figs. 265 and 266). 

 Young shoots, coming from wounds, also 

 have needle leaves. Occasionally, indi- 

 viduals of a species which has appressed 

 leaves revert more or less completely to 

 the primitive type with needle leaves. 

 Such forms, called Retinospora, retain 

 rather persistently the needle leaf. Junip- 

 erus, which has some species with needle 

 leaves and some with appressed leaves, 

 has given rise to many horticultural 

 forms. In beds of seedhngs the horticul- 

 turist watches for desirable variants, and 

 propagates them by grafting or by cut- 

 tings. 



It is evident that, as far as living coni- 

 fers are concerned, with the possible ex- 

 ception of broad-leaved forms, the needle 

 leaf, borne on a long shoot, is the most 

 primitive type of foliage, from which 

 concrescent leaves, leaves borne on spurs, 

 fused leaves, and phylloclads are later 

 derivatives. 



Nearly all conifers are evergreen, Larix 

 and Taxodium being the only deciduous 

 American genera. Taxodium distichum 

 is always deciduous, and I was told 

 that in northern Mexico T. mucronatum 

 is deciduous. However, the "Big Tree of 



Fig. 261. — Pinus laricio: A, 

 young long shoot with numer- 

 ous spur shoots showing the 

 pairs of needle leaves just break- 

 ing through scale leaves; B, ma- 

 ture long shoot with several 

 spurs, each bearing two needle 

 leaves. Below the lowest spur 

 with two complete needle leaves 

 are two scars left when the 

 spurs, with their leaves, had 

 fallen off; both natural size. 



