NATURAL DWARFING 



Severe Climate and Lack of Food Produce Remarkable Differences in Plants 

 Effects Probably Not Hereditary Dwarfed Arbor-Vitae 



Albert A. Hanskx 



Department of Botany, Pennsylvania State College 



W\\\L\ plants <:;ro\v in jjoor soil, 

 where they do not get enough 

 food, they arc likely to be 

 dwarfed. Some writers call 

 this dwarfing "nanism;" others reserve 

 that name for the rarer form of dwarf- 

 ing which is ajjijarcntly due to some 

 abnormalit\- in the mechanism of hered- 

 ity, and which is exemi:)lified by Oeno- 

 thera nanella, a dwarf mutation from 

 Lamarck's Evening Primrose. This 

 dwarf comes true to seed, as do most 

 other mutant dwarfs. 



Most of the dwarf jjlants found in 

 nature, however, are small only be- 

 cause of lack of nourishment. An 

 example is the mesquite iProsopis 

 jiiliflora) of the southwestern States, 

 which is famed as an indicator of sources 

 of water supply, because of the water 

 seeking propensities of its roots. In 

 favorable locations the mesquite is an 

 average tree in size, but it becomes a 

 gnarled and scraggy shrub when grow- 

 ing in an environment which contains 

 insufllcijnt food and moisture. 



The art of the oriental gardeners in 

 producing the spectacular dwarf "Trees 

 of Life" is dependent upon the starva- 

 tion of the entire plant. S])ruces, 

 oaks, orange, arbor-vitae and other 

 trees have been made to bear fruit 

 when less than two feet in height. 

 These pygmy jjroducts formerly sold 

 for fabulous j^rices, hundreds of dollars 

 sometimes Ijcing ]^aid for a single ])er- 

 fect specimen. Professor Sorauer, of 

 Berlin, mentions a dwarf si)ecimen of 

 Thuja ohtusa which cost S87.50, the 

 value evidently being so placed within 

 recent years. These dwarf trees are 

 in great favor throughout China, where 

 it is said every house of any ])retensioii 

 whatever exhibits one or more speci- 



mens. The dwarfing tendenc\', accord- 

 ing to Staunton, is jjerpetuated when 

 the plants are jjropagated vegetatively, ' 

 but conclusive experimental data u]^on 

 this point do not seem to be available. 



American gardeners have dui)licated 

 the jjroducts of the Jai)anese and Chin- 

 ese by simply starving the i)lants in 

 small pots and severely jjruning the 

 root system. Frequent transplanting 

 is necessary in order to produce the 

 best results. The crown is kept pro- 

 portionately cut back in order that the 

 tree may not be injured by the loss of 

 too much water in transjjiration. The 

 limiting of the soil content is perhaps 

 the biggest factor in the jjroduction of 

 dwarfs. 



The general j^rincipL'S of dwarfing 

 as herein stated were confirmed in 

 nature in a very interesting manner 

 by plants recently collected by the 

 writer. Growing in almost soilless rock 

 crevices on the l)arren shores of Lake 

 Su])erior, a ]n'gmy forest of severely 

 dwarfed spruce, Picea martana, and 

 arbor-\-itae. Thuja oecidentalis, was dis- 

 covered. Eighteen annual rings were 

 counted in a sjjruce slightly more than 

 a foot high, and fifty-three rings were 

 re\^ealed by the compound microscope 

 in the trunk of an arbor-vitae a foot 

 tall. These ]:)lants were dwarfed prob- 

 ably by both the lack of water and of 

 necessary minerals. 



The exi)eriments of MoUer with a 

 wild grass, Bromus mollis, indie-ate that 

 this form of nanism is not hereditary. 

 He produced progeny of large size from 

 the seed of dwarf i)lants. However, 

 under equal vegetative conditions, he 

 found that seed from nonnal ])lants 

 l)r()duced more vigorous s])ecimens than 

 (lid seed from dwarf |)lants. 



'Manual of Plant Diseases — Sorancr. Vol. 1, i)arl 11, p. 142. 

 160 



