334 • IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



one genu's, viz. Prunus, showed marked swelling of the fibers as a 



result of maceration. Prunus Davidiana was the most swollen 



species. This affected the diameter, but apparently did not afifect 



the length. 



A survey of the measurements shows first of all a striking dilifer- 



ence between the lengths of fiber in Gymnosperms and Angiosperms. 

 The greater length of fiber in the former group doubdess stands in 

 relation to the demands of water conduction in these ductless plants. 

 But when Pimis pondcrosa, Abies halsamea, Thuja occidentalis and 

 Juniperus virginiana all show lengths of fiber comparable with 

 those of Angiosperms, one is at a loss for an explanation. It must 

 be noted that Pinus ponderosa and Juniperus virginiana are in- 

 habitants of dry soils, and Abies balsaniea and Thuja occidentalis 

 prosper in bog soils. All may be considered xerophytic. The re- 

 maining Gymnosperms in our list must be considered as mesophytes. 

 But Taxodium is a bog plant, and has very long fiber. Comparing 

 the species of Thuja, the one from the moist region of the north- 

 west coast, T. plicata, shows much the longer fiber. 



Among Angiosperms there is a striking uniformity in length of 

 fiber in the apetalous series, where the measurements nearly all 

 average above one millimeter. In the higher orders, the lengths 

 are nearly all below one millimeter. Liriodendron, which in some 

 respects is a relatively primitive species, and is certainly very 

 ancient, has a fiber a. little less than 1 mm. in length, i. e. inter- 

 mediate between the principal groups. Platanus and Fraxinus, 

 both very unique among their near relatives from the standpoint of 

 floral structure, are also decidedly aberrant in fiber length, Prunus 

 Davidiana is similarly aberrant. On the whole, it would seem that 

 fiber length varies very widely within narrow taxoilomic limits. 



From the standpoint of the uses of wood, the length of fiber 

 alone is not a guide to weight, strength or elasticity. Western 

 spruce, so valuable for aeroplanes, has the longest fiber on our list. 

 But Taxodium is a close second. Oak, ash, elm, birch and cotton- 

 wood are remarkably similar in fiber length. 



Probably the length of fiber in wood has more relation to its 

 value for paper plup than for any other practical use. It is well 

 known that coniferous woods make the best pulp, and of these 

 spruce pulp brings the highest price. This is due to the length of 

 the fibers. Spruce and Sequoia, however, proved to be the most 

 difficult woods to break down by the maceration process used by 

 us. In view of the excellent fiber produced by Picea sitchensis, 

 attention should be called to the tremendous waste of the wood 

 of this species in stumps and tops by the lumbering methods current 



