64 BOOKS AND CURRENT LITERATURE 



Germination and Early Growth of Forest Trees. — In a recent 

 paper', Boerker presents what is perhaps the first American. pubHcation 

 on the scientific side of forest nursery practice, the work being based 

 on the greenhouse germination and growth of many American forest 

 tree species. The work is divided into three parts : the effect of habitat 

 factors on germination; the effect of habitat factors on stem and root 

 development, and the relation of the size of seed on germination and 

 development. 



The author finds that from the germination in three different soil 

 moistures he is able to divide the trees of each region into three classes. 

 The xerophilous species germinated in all three soil moistures, the 

 xero-mesophilous group in the two moister soil cultures, and the meso- 

 philous species germinated only in the soil containing the most moisture. 

 In general, the drier the soil the longer germination was delayed, though 

 the total length of the germination period is decreased as is the final 

 germination per cent. Shade affected the germination by decreasing 

 the time necessary for its initiation and by increasing the length of 

 the germinating period. In all three groups germination began first 

 in the dense shade and last in full light with the longest germinating 

 period and highest germination per cent in the dense shade. Sand 

 gave a more rapid germination, a higher final germination per cent, 

 and a longer period of germination than did either gravel or loam. Sand 

 and gravel accelerate germination while loam retards it, due more to 

 the lack of oxygen than to a difference in soil moisture. The larger 

 sized seeds of Pinus ponderosa and Pseudotsuga taxifolia gave a higher 

 germination per cent and produced larger seedlings than did the smaller 

 sized seeds. From east to west, the seeds of these species germinated 

 earlier, the rapidity factor was greater and the germination period was 

 shorter, while in the case of P. ponderosa the size of the seed increased. 



In this discussion of the habitat factors on stem and root develop- 

 ment, the author brings out no points that are unfamiliar to the forest 

 nurseryman and practitioner, and the results attained with four species 

 are too conflicting for definite conclusions. While the work is interest- 

 ing from many standpoints to foresters and well worth a perusal by 

 students of plant life the data are too meager and the number of seeds 

 on which the work is based too few, especially in such species as Liboce- 

 drus decurrens, to eliminate errors and to warrant adopting in toto the 

 conclusions which are brought forward. The germination curves 

 which accompany the text are very instructive. — Edw. N. Munns. 



'Boerker, Richard H., Ecological Investigations upon the germination and 

 early growth of forest trees. Diss. Univ. Neb. Lincoln, Nebraska, 1916. 



