OBSERVATIONS ON CANADIAN CONIFEE^. 23 



have an average diameter of 0-098 mm. In specimens of this species from tlie Sargent col- 

 lection of United States woods, I find the resin-passages to be also very scattering, with an 

 average of seven per centimetre and a diameter of 0'093 ram. The onl}'' essential difference 

 appears to be in the nnmber of resin-passages, which in the case of the Kootanie specimens 

 are twice as many as in specimens from other localities, bnt still very few relatively to what 

 is found in most of the pines. 



In this case, therefore, as in Pseudotstiga, the resin-passages afford no explanation of the 

 question under consideration, nor do they appear to bear any relation to the Ijreaking up of 

 the structure in process of desiccation or decaj'. 



PiNDS PONDEROSA. 



(Plate I., fig. 6.) 



Desiccation in the log for ;i period of three months resulted in establisliing a nuiiil)er of 

 star shakes, which in a few instances were connected by irregular tangential fractures. The 

 additional influence of furnace heat produced no sensible change beyond causing the frac- 

 tures already established to become wider and prcnnoting a stronger contraction in volume, 

 which has continued at a diminishing rate up to the present time. The "shaking" was, 

 therefore, much less than in either of the previously considered cases, and was at its most 

 extensive limit no more than may ordinarily' be found in the seasoning of woods under 

 similar conditions. Exudation of resin was noted in the sap wood only, but was at no time 

 copious. 



Under the hatchet or chisel the wood split with tolerable facility, Ijut always most 

 readily in a radial direction, the line of fracture being determined l)y the position of tlie 

 instrument or by the direction and position of a medullary ray only. 



The section removed from the log, after three months of desiccation, showed no farther 

 alteration ujion being submitted to more powerful desiccating influences for an additi(nial 

 period of one month, showing that, as in the previous cases, seasoning in the log is an 

 essential condition to the establishment of strongly developed shakes. 



Section a, submitted to maceration for a period of one month, and desiccation two and 

 one-half months, and section ft, macerated for four and one-half months and afterwards 

 desiccated, showed no change whatever, although in each case the maceration was attended 

 by a copious fungoid growth, the mycelia of which penetrated ihe structure freely. 



The growth-rings are rather prominent, varying from 1-0 to 3'.5 mm. in width. The 

 summer wood is rather prominent, somewhat resinous and dark, generally from one-fifth to 

 one-half the spring wood, rarely exceeding it ; or, in other words, thin, rarely equal to one- 

 half the growth-ring. Microscopical sections show the resin-passages to be scattering, and 

 in no ease localized in bands or plates. The}' average thirty-six to the square centimetre, 

 and have an average diameter of 0'124 mm. 



In a specimen of this wood from the Sargent collection of United States woods, the 

 scattering resin-passages are found to average sixty-nine per square centimetre, with an 

 average diameter of 0'172 mm. Thus it appears that in our Kootanie specimen the resin- 

 passages are not only much smaller than usual, but that they are, in round numbers, about 

 half as numerous ; so that instead of there being a special modification in the direction of 

 excessive resin deposits, the alterations take precisely the ojiposite direction. 



