[pENHALi.ow] NOTES ON TERTIARY PLANTS 71 



which at first sight involved an element of dilllculty in diagnosis. 

 The swelling of the secondary walls thus observed is precisely of the 

 nature of that Avhieh we are familiar with as resulting from the pro- 

 longed action of an alkali, especially when aided by heat, and it seems 

 to give very clear proof that the woods must have been immersed in the 

 water of hot springs containing a small proportion of alkaline silicates, 

 with a large proportion of free alkali. From this we are enabled to 

 determine that the general sequence of events in the process of petrifica- 

 tion must have been: — 



1. The operation of somewhat limited decay. 



2. The action of hot alkaline solutions on the tissues. 



3. The action of alkaline silicates. 



The only other instance of similar alteration which we have met 

 with was observed in the ease of Taxodium distichum from the Lignite 

 Tertiary of the Great Valley Group in the Northwest Territories. In 

 that case, however, the subsequent silicification had been carried much 

 farther, so that the whole structure was converted into a mass of silica, 

 which could only be cut on the lapidary's wheel. 



Mr. Oscar H. Healy, from whom tbc specimens were obtained in 

 the first instance, states that the formation is '"' Late Quaternary," and 

 that it dates from a period of exce-sive humidity, apparently closing 

 the '^^Intermediate Stage"' of glaciation, probably about "lowan" in 

 age. 



The Pscudotsuga of these deposits is well within the present range 

 of the species which extends along the coast ranges into siouthern 

 California, and it is, in fact, within the region of greatest development. 

 of that genus. 



Juniperus californica, on the other hand, indicates that the species 

 has receded from its former range. At the present time it is unknown 

 ir Humboldt county. According to Prof. Sargent, its greatest 

 northern extension is to be found in the valley of the Sacramento, 

 whence it ranges southward along the coast ranges. It is therefore 

 at the present time a somewhat more southern typo than formerlv, and 

 we are therefore led to infer that the climate of Humboldt county was 

 originally somewhat warmer than at present. This would agree with 

 our knowledge of the recession of Pseudotsuga and Sequoia within late 

 Tertiary time, and would seem to point to the operation of the same 

 general causes. 



Recent explorations of the Interglacial beds at Toronto have 

 brought to light an additional amount of material, which, while it does 



