Variations in Anatomical Structure 667 



In a paper published in 1914 Shepard* and one of the writers 

 questioned the general applicability of Sanio's first law, since no 

 constant tracheid length could be found in Abies concolor Lindl. 

 and Gord., Pinus strobus L., P. palustris Mill., Picea rubens Sarg., 

 and Tsuga canadensis Carr. In the investigated specimens of 

 these species, the tracheids increased rapidly in size for a number 

 of years (30-60) , and in succeeding years no constant length was 

 attained. On the contrary, the dimensions were subject to pro- 

 nounced fluctuations of varying magnitude and duration. Sanio's 

 curve for a basal section of a 105-year-old specimen of Scotch 

 pine and that of Shepard and Bailey for a similar section of a 230- 

 year-old specimen of Longleaf pine are given in figure 1. More 

 recently the results of Shepard and Bailey have been corroborated 

 by Miss Gerry ,^ who has made a very detailed study of Longleaf 

 pine and Douglas fir. 



In his study of arborescent and shrubby Dicotyledons, Sanio^ 

 reached very different results in regard to the variation in the size 

 of the xylem elements in these plants from those which he had 

 previously published in regard to the conifers. His measurements 

 show that the fibers increase in length in succeeding annual rings 

 in Caragana arborescens, Sophora japonica, Saroihamnus scoparius 

 Acacia longifolia, Carpinus Betulus, Quercus pedunculata, Cornus 

 sanquinea, Rhamnus cathartica, and Ficus elastica. The length 

 of the fibers remained constant, however, in Mahonia aquifolium 

 and Berberis vulgaris, as did that of the vessel-segments in these 

 species and in his species of Ficus, Caragana, Sarothamnus, Acacia, 

 and Sophora. In only one species, Quercus pedunculata, did Sanio 

 secure material from a specimen of sufficient size or maturity to 

 afford results comparable to those secured from his study of 

 Scotch pine. Furthermore, his limited number of measiirements 

 were confined to the earliest and last formed rings, and, therefore, 

 afford no evidence in regard to the behavior of the elements at 

 intermediate stages in the development of the plants. 



* Shepard, H. B., and Bailey, I. W. Some observations on the variation 

 in length of coniferous fibers. Proc. Soc. Am. Foresters, Vol. IX, No. 4, 1914. 



* Gerry, Eloise. A comparison of tracheid dimensions in Longleaf pine 

 and Douglas fir, with data on the strength and length, mean diameter and 

 thickness of wall of the tracheids. Science, Vol. XLIII, No. 1106, p. 360. 



* Sanio, Karl. Anatomic der gemeinen Kiefer {Pinus silvestris L.) II. 

 Jahrb. Wiss. Bot., Vol. IX, pp. 50-126. 



