CONIFERALES 253 



a great display of resin canals, through a lesser display to a condi- 

 tion in which there are none at all. Sometimes such a series can be 

 read as one of increasing complexity, or of a continuous simplifica- 

 tion. Jeffrey's experiments, causing the canals to appear in regions 

 from which they are normally absent, as a response to wounding, 

 indicate that the series should be read from the complex to the 

 simple. His claim that wounding causes a reversion to a more ancient 

 condition seems well founded. The evidence from fossils, as far as it 

 goes, is in favor of Jeffrey's theory. 



The leaf. — The leaves of Coniferales, in comparison with those of 

 the Cycadophytes, are very small, even smaller than those of the 

 Cordaitales. There are no compound leaves in the order. The small 

 simple leaf has led some to look to the lycopods for the origin of the 

 group; but, in spite of the small size of the leaf, the leaf gaps are 

 present and well developed throughout. As far as this feature is con- 

 cerned, the Coniferales belong definitely to the Pteropsida rather 

 than to the Lycopsida. It has been said that the Coniferales are 

 palingenetically megaphyllous, but coenogenetically microphyllous; 

 which means that their remote ancestors had large leaves which, 

 in the course of evolution, have become reduced to small leaves. 



The arrangement of the leaves is spiral, except in the Cupressaceae 

 where it is cyclic, and in Microcachrys, which also has the cyclic 

 arrangement. 



The dominant leaf of the order is so small, so slender and rigid, 

 and so sharp-pointed that it is commonly called a ''needle leaf" 

 (fig. 258). But there are many conifers, belonging mostly to the 

 Southern Hemisphere, which have broad leaves, not at all needle- 

 like. These belong, mostly, to Podocarpus and the Araucariaceae 

 (fig. 259). The leaves of Podocarpus wallichianus reach a length of 

 12.5 cm. and a width of 3.5 cm. In some species of Araucaria the 

 leaves are broader and nearly as long. 



In the large leaved forms, there is no differentiation into long 

 shoots and spur shoots, all leaves being borne upon long shoots. 

 Some forms with needle leaves have only long shoots, Hke Abies, 

 Picea, Tsuga, Juniperus, etc., while others, like Pinus, Cedrus, Larix, 

 and Pseudolarix, have both long and spur shoots. 



In Larix, in the first year's growth of stem or branch, there are no 



