1889.] MICEOSCOPICAL JOURNAL. 275 



with blotting-paper. For the determination of the fibres a magnifying 

 power of 300 diameters is best adapted, but, for ascertaining the rela- 

 tive proportion of the fibres, one of 120 diameters, that permits of tak- 

 ing in a wider surface, is preferable. — Gutenberg yourjial. 



BIOLOGICAL NOTES. 



By Prof. J. H. Pillsbury. 



NOlil HAMPTON, MASS. 



Strength of Wood. — Certain tests made at the car-shops of the 

 Northern Pacific Railroad at Tacoma, Wash., show that a bar of wood 

 2x4 inches and four feet long, resting on supports three- feet nine inches 

 apart, broke under the following strains, viz., yellow fir, six years ex- 

 posed to the weather, 3,062 pounds : new soft 3'ellow fir of fine grain, 

 3,063 pounds ; old and hard yellow fir with coarse grain, 4,320 pounds ; 

 new .fir from the butt of the trees, and of coarse grain, 3,635 pounds ; 

 Michigan oak, 2,428 pounds. Is not this contrary' to the usual repu- 

 tation of oak wood .' 



Annual Rings of Trees. — Prof. Hartwig is quoted as authority for 

 the statement that trees cut three or four feet from the ground often 

 show a larger number of rings of annual growth than when cut at the 

 usual distance from the ground, the deposit of tissue failing to be made 

 in the latter region. 



o 



Grape-Vine Diseases. — The culture of the grape in Algeria, ac- 

 cording to the report of the consul-general to the foreign office of the 

 British government, is beset with great difficulties. Beside the phvl- 

 loxera. the alise. and such parasites as oidium, anthrachosis, pereon- 

 ospora, and chlorosis have caused a loss of nearlv one-third of the crop. 



o 



Autumn Colors. — In addition to the chlorophyll of plants, there is 

 generally present in their cells a small quantitv of certain other color- 

 ing matters as xanthophyll, eiythrophvll (yellow and red coloring mat- 

 ter) , both of which are derived from chlorophyll by the chemical forces 

 of the plant, but which are in so small proportions as to be more or 

 less completely covered up by the presence of the chlorophvU. If for 

 any cause these are increased in quantity they give their peculiar color 

 to the leaves, as is the case with foliage plants. In the normal growth 

 of the plant, especially of perennial plants like our forest trees, the early 

 summer is the period of rapid growth. Later in the season the cells 

 formed in the early summer become hardened into wood and active 

 growth ceases. At this time the portion of the chlorophyll is changed 

 to xanthophyll and erythrophyll and a portion withdrawn to other parts 

 of the plant. This leaves the bright colors in sole possession of the cells 

 and gives the peculiar tints to the autumnal leaves. These changes are 

 affected by the variations of the season. When the season is very dry 

 the nutrition of the plant is interfered with and the growth ceases at an 

 abnormally early date, and the colors make their appearance earlier than 

 usual, but are less brilliant. Earlv frosts destrov the life of the leaf and 



