180 Forestry Quarterly. 



BOTANY AND ZOOLOGY. 



Referring to Fricke's article on "Tolerant 

 Tolerance and Intolerant Species, a dogma scientifi- 



of cally unproved" (see Quarterly, vol. II, p. 



Species. 226), Dr. Cieslar publishes the results of 



investigations of this question carried on 

 for eighteen years. Fricke denied the existence of varied toler- 

 ance of species but recognized tolerant and intolerant forms in 

 the same species ; whether this adaptation was habitual or se- 

 cured through the life of the individual he did not state. 



It has been generally accepted, and demonstrated by Hessel- 

 mann through exact investigation, that every species can endure 

 more shade on fresh sites, but if compared on the same site a 

 graded difference of this capacity among the species can be as- 

 serted. 



In 1890 Cieslar started 10 beds, each sown in drills with Spruce, 

 Black and Scotch Pine, and Larch, eight of the beds being 

 shaded with lath screens of varying closeness so as to secure 

 from 25 to 75 per cent, of shade. One of the remaining beds 

 was covered with moss between the drills without shade, the 

 other left entirely open. While for most beds laths of 1 cm. were 

 used, one was covered with a screen of 2 cm. and another of 3 

 cm. lath, which was found afterwards to give different results 

 from those covered with the 1 cm. lath screens, namely, relatively 

 better ones, for here the actual light passing through is larger 

 than the theoretical 50 per cent. The results of the denser, darker 

 shade are also influenced by the fact that the soil here is kept 

 moister. The effect was determined by very accurately meas- 

 uring with Friedrich's precision xylometer the volume of 100 

 seedlings and comparing the volumes percentically to those of 

 the moss covered bed; also comparing the length of the plants 

 percentically with those of the least shaded bed. 



The results are given in tables from which we bring an extract. 



