262 



GYMNOSPERMS 



leaf trace is a primitive feature, because the traces in the cotyledons 

 of such characteristic forms as Finns and Ahies are single. In fact, 

 the traces of the cotyledons are single in all of the Taxodiaceae and 

 Cupressaceae, except, occasionally, in Cnpressns tornlosa. They are 

 double in Araucariaceae. In all cases the cotyledonary strands con- 

 nect with the poles of the root. 



The root and Jiypocotyl. — Many conifers, like Finns syhcslris and 

 F. marilima, are anchored by a powerful tap root ; but in some pines, 

 like F. montana, and in several other genera, 

 the primary root soon aborts, and practically 

 the only anchoring is by lateral roots. Those 

 which have no strong tap root, especially 

 those of the Ficea excelsa type, are more 

 easily blown down; but in many the lateral 

 roots are wide spreading, and often extend 

 obliquely downward, thus afTording consider- 

 able stability. 



Besides the long roots of both the tap and 

 lateral type, there are short roots, which are 

 small and often profusely branched. These 

 roots, which do not attain any great age, 

 often failing to reach the secondary wood 

 stage, are the principal absorbing organs of 

 the plant. The profusely branched roots fre- 

 quently contain mycorhiza, but there are no 

 ectotrophic mycorhizas in the Araucariaceae, 

 although cells of the cortex are often filled with mycorhizas of the 

 endoi)hytic type. In the Podocarpaceae there are root tubercles,'^'^ 

 resembling those of the Leguminosae, and such roots have root hairs, 

 though in some genera similar roots have no root hairs. It has been 

 claimed that there are no root hairs on coniferous roots; but the 

 observations were very superficial, for root hairs are almost invari- 

 ably present near the tip (lig. 272). It is a partial excuse for the mis- 

 take that the root hairs are confined to a very small region at the tip 

 and break off so easily that they are lost unless the washing is very 

 carefully done. In the series from which fig. 272 was drawn the 

 region of root hairs was not more than i millimeter in vertical extent. 



Fig. 266. — Thuja occi- 

 denlalis: two cotyledons, 

 Juvenile leaves, and later 

 appressed leaves; natural 

 size. 



