E>^DOGENOUS TREES. 



[Monocotyledons. ) 



Endogenous trees are those that increase from within. 

 Their elemental parts are similar to those of exogenous trees 

 but the arrangement of such parts differs in that the newer 

 fibres of the Endogen intermingle with the old, pass through 

 a pith-like tissue, and cause cross-surfaces to appear as dotted, 

 whereas the new material of the Exogen is deposited altogether 

 and upon the outside of the old, their sections exhibiting rings 

 or layers. The Palms, Yuccas, Cornstalks, and Bamboos are 

 of the endogens. Bark is unusual on trees of the series. 



Endogenous woods are hardest and most compact at cir- 

 cumferences. The stems of palm trees are solid, but those of 

 some of the grasses, particularly those that grow quickly, are 

 hollow.* The tube or canal, when existing, is due to sluggish- 

 ness on the part of the central pith, which, developing more 

 slowly than the outer tissues, finally ruptures and disappears 

 at the center. There are also more or less permanent joints 

 or knots, t such as are made familiar by the canes and bam- 

 boos. The stems of Endogenous plants are seldom cut up 

 into lumber, but are used in segments, or else entire, as for 

 troughs or piles. | The use of Palm wood must be more or less 



* The Bamboo, which is a grass, is hollow, while the cornstalk, which is also 

 a grass, is not. 



■j- The knots of endogens correspond to the nodes of exogens. Spaces between 

 the nodes, known as internodes, mark the annual lengthening. Knots are places 

 whence leaves have emerged. 



I Palm in marine work appears to repel the teredoe. This is probably because 

 of the porous character of the wood. See "Marine Wood Borers," Trans. Am. 

 Soc. C. E., Vol. XL, pages 195 and 204. 



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