Periodical Literature. 181 



Spruce. Austrian Scotch Larch. 



Pine. Pine, 



vol. Igth. vol. Igth. vol. Igth. vol. Igth. 



Unshaded, 58 79 145 100 146 108 68 120 



with moss, .... 100 116 100 163 100 154 100 135 



Shaded .25 79 100 101 100 69 100 67 100 



■ 33 92 103 78 no 70 103 44 109 



.40 90 106 74 109 68 118 56 122 



• 50 80 in 73 131 41 140 46 143 



2 cm. 50 76 109 62 125 34 148 31 134 



3 cm. 50 87 108 67 113 53 115 44 125 



.66 64 121 34 162 21 169 21 151 



• 75 54 133 27 155 19 184 13 176 



The author argues: If the product of the different conifers 

 with decreasing light decreased in equal proportion we would 

 have to give up the terms "tolerant and intolerant species;" if, 

 however, with the same degrees of shade the product of some 

 were more and that of others less, then the distinction has silvi- 

 cultural justification. Thus, if the Larch can, when three-quar- 

 ters shaded, produce only 13 per cent, of the volume attained 

 when unshaded, while the Scotch pine produces still 19 per cent., 

 and the same relations are found persistently with other degrees 

 of shading and with other species, then the proof seems incon- 

 trovertible that tolerance is a specific quality. The smaller the de- 

 pression of volume production in a species with a given degree 

 of shade, the smaller is the need of light by that species, the more 

 shade-enduring or tolerant is the species. 



The variation of the beds covered with broader lath is strik- 

 ing, and a hint for nursery practice. 



Another interesting result is the influence of the shade on 

 length growth. All species show increase in length with increase 

 of shade — the well known etiolation influence — but the shade- en- 

 during respond less to the stimulus than the light-needing. While 

 Spruce increased its length under the densest shade only 33 per 

 cent, pine and larch increased it by 55, 84 and 76 per cent, re- 

 spectively, the plants of the last two beds of these being very 

 spindly and weak, absolutely useless. This is another proof of 

 the specific character of tolerance. 



The excellence of the growth on the unshaded, moss-covered 

 bed is specially noticeable, and argues for this method of nursery 

 practice and also for the relation of tolerance to moisture condi- 

 tions. 



Check tests instituted in 1894 and 1896 with all species under 



