internal causes of disease 329 



Malformations and Monstrosities 



Hugo de Vries has shown that malformations and monstrosities 

 do not arise as a result of variations, but may be looked upon as muta- 

 tions. His tricotylous, hemisyncotylous, syncotylous, and amphi- 

 syncotylous races are proof of this statement. Fasciation in its 

 simplest form consists of a flat, ribbon-like expansion of stem, 

 branch, flower clusters, flowers and fruits which may be cylindric 

 below, but flattened above. This is one of the most common of all 

 malformations and by numerous experimental cultures the fasciation 

 has been found to be heritable. Spirally twisted plants are more 

 striking malformations than fasciations. Valeriana officinalis is 

 one of the best-known examples displaying spiral torsion. It is also 

 displayed in a teasle. Dipsacus silvestris torsus, twisted sweet william, 

 Dianthiis barbatus, dark-eyed Viscaria, Viscaria oculata. Such mal- 

 formations de Vries has shown to be truly heritable. (Pleiphylly is 

 that condition where two or more leaves arise in place of a single one.} 

 Such we find in the ever-sporting races of clovers, where four, five, 

 six, seven, or even eight leaves appear instead of the normal three. 

 The presence of three leaves in a whorl, or of three cotyledons, as above 

 noted, is called polyphylly. Shull has shown that the ascidial 

 leaflets of the white ash, Fraxinus americanus, are heritable. Pistil- 

 lody is demonstrated in the appearance of imperfect pistils in place of 

 stamens, as in the poppy. When colored flower parts become green, 

 this condition is known as antholysis, or chloranthy, and is illustrated 

 in green roses and green dahlias. This condition and petalody and 

 sepalody are transmitted. Peloria, where a normally zygomorphic 

 flower, as in the toad-flax, Linaria vulgaris, is transformed into a regular 

 flower with five spurred petals instead of one spurred petal, is 

 another example of monstrosities which are heritable. 



The history of Cytisus Adami which originated as a graft hybrid 

 is of interest in connection with the study of Chimaeras. Hybrids that 

 arise by vegetative reproduction, where scion and stock are mutually 

 affected, are known as graft hybrids. The origin of Cytisus Adami 

 seems to have been as follows: a shoot of Cytisus purpureus was 

 grafted on a stock of Cytisus laburnum; from this were produced many 

 shoots, one of which grew vigorously, and developed larger leaves 

 than those of C. purpurcus and from this shoot plants were propagated 



