526 BOTAXICAL GAZETTE [june 



factors in determining the succession. The probable history of the heath is 

 well discussed and the diagrams are decidedly good and appropriate. 



A remarkable instance of the vitality of moss protonema is recorded by 

 Bristol, 6 who found resting protonemal cells, rich in oil, in dry soil stored in 

 air-tight bottles for 46-49 years. In cultures these grew and produced pro- 

 tonema of the ordinary type. 



In a series of notes West? has recorded the bryophytes and lichens found 

 upon trees in parts of Scotland, Wales, and Ireland, and has arranged them 

 according to abundance. He has found the percentage ratio of some of the 



ifc 



tar tar ea 2, and Platysma glaucum 1. — Geo. D. Fuller. 



fuligi 



Variations in wood structure.— Several recent articles have called in ques- 

 tion some of the "laws of Sanio" for variation in the size of tracheids in 

 conifers, more particularly that law which states that tracheids increase in 

 size from the pith radially outward until they reach a definite size, which 

 remains constant for the following annual rings. Shepard and Bailey 8 

 found the gradual increase in size up to 30-60 years, but in succeeding years 

 no constant length was attained. Later the same authors maintained their 

 points in this journal. 9 



Their results were for the greater part confirmed by a detailed study of 

 Pinus palustris and Pseudotsuga by Miss Gerry, 10 who also finds the longest 

 tracheids in the early spring wood and the shortest in the late wood. Lee 

 and Smith 11 now supplement this with an extended study of Pseudotsuga from 

 British Columbia. Their results, in general, agree with those already cited 

 except that after a gradual and fairly rapid increase up to the age of 50 years 

 the tracheid length varies comparatively little, but tends to increase slightly. 

 They also find an increase in tracheid length up to 42 ft. above the ground, 

 and then a gradual decrease up to 154 ft., where the measurement ceased. It 

 is interesting also to note that trees from the coast region appear to have slightly 

 longer tracheids than those from the mountains. 



6 Bristol, B. Muriel, On the remarkable retention of vitality of moss protonema 

 New Phytol. 15:137-143. 19x6. 



7 West, \V., Ecological notes; chiefly cryptogamic. Jour. Linn. Soc. 43o7-85 



1915- 



\RD 



length of conifer fibers. Proc. Soc. Amer. Forest. 9: 1914. 

 9 Bot. Gaz. 60:66-71. 1915. 



10 Gerry, Eloise, A comparison of tracheid dimensions in longleaf pine and 

 Douglas fir. Science 43:360. 1916. 



11 Lee, H. N., and Smith, E. M„, Douglas fir fiber, with special reference to length. 

 Forest Quart. 14:671-695. 1916. 



