Current Literature 527 



younger seedlings in nursery beds need some kind of protection 

 from evaporation. 



The reviewer cannot see how the above conclusion of the 

 authors logically follows the data presented, since no evidence 

 is presented that the greater loss of water has any detrimental 

 effect upon the young seedlings. Although it is a common 

 method of procedure among investigators of this subject, the 

 reviewer would question in all cases the value, for comparative 

 purposes, of conclusions based upon transpiration in relation to 

 the dry weight of plants of different ages. As a plant grows 

 older, it has a larger proportion of cells not employed in the 

 conduction of water or in the loss of water vapor. By adding the 

 dry weight of these to the calculation, one naturally reduces the 

 ratio of transpiration to the dry weight of the entire plant. The 

 leaves, of course, in a seedling form a larger percentage of the 

 total dry weight than in a plant a few years older. Suppose a 

 hypothetical case of two plants of different ages and sizes trans- 

 piring identical amounts of water, the relation of transpiration 

 to the dry weight of the two plants could not be the same. 



C. D. H. 



The Testing of Forest Seeds During Ttventy-jive Years. By 

 Johannes Rafn. Printed for Private Circulation. Pp. 91. 



The well-known head of the commercial Scandinavian Forest 

 Seed Establishment gives in this brochure the results of 25 years' 

 experience in testing forest seeds in connection with his business. 

 The actual germination tests were made in the Jacobsen germi- 

 nating apparatus at the Danish Seed Testing Station, a State 

 institution which carries on about 12,000 tests of agricultural, 

 garden and forest tree seeds in a season. The results of the 

 germinating tests are given under the following headings : weight 

 of 1,000 seeds in grams, number of seeds per kilogram pure 

 seed, per cent purity, per cent germinating capacity (germinated 

 and sound), real value and the course of germination (the per 

 cent germinated in 5, 10, 20, 30, 60, 100, and 100+ days). The 

 real or practical value given in the tables is the per cent purity 

 multiplied by the actual germinating per cent plus the sound but 

 not yet germinated seeds, at the time the test is closed. Such re- 

 sults are given for about 150 species and varieties of conifers 



