CHAPTER XXVII 

 CLASSIFICATION OF PLANT ABNORMALITIES 



The older botanists prior to the pubHcation of the important work 

 of Maxwell T. Masters in 1869 gave little attention to abnormalities in 

 plants. Linnaeus treated of them to some extent in his ''Philosophia," 

 but it is mainly to Augustin Pyramus de Candolle that the credit is 

 due of calling attention to the importance of vegetable teratology, as 

 throwing light upon normal structure and functions. Until the epoch- 

 making work of de Vries on plant mutations drew attention to the 

 absolute necessity of experimental methods in the study of normal and 

 teratologic plants, the field of vegetable teratology was the concern of 

 the plant morphologist and the different abnormalities were studied by 

 comparative morphologic methods. Hugo de Vries and several of 

 his co-workers pointed out that many abnormal forms are heritable and 

 this suggested that the line of approach in their study was through 

 experiments in breeding these forms to discover their origin and 

 true character. This has been done with a few forms, but the whole 

 field should be worked by some competent geneticist, who would devote 

 his life to the undertaking. Without further discussion, it has been 

 thought advisable to put in a form accessible to American college 

 students, a glossary of the more important terms used in teratology. 

 With the exception of a few additions the terms given in first volume 

 of " Pflanzen-Teratologie" (1890) by Dr. 0. Penzig are here translated 

 from the original, as serving as an outline of teratology for American 

 students. 



Abortion (Masters and English authors; Abortus, German Avortion 

 or Avortement, French)— Stunting of an organ, that is the exceptionally 

 small formation of the same, whereby the form remains unchanged. 

 The German and French authors use the same expression very fre- 

 quently for the cases where a certain organ is entirely suppressed and 

 does not make an appearance. 



Acaiilosy. — Acaulosia is the diminution in the size of the stem, for 

 absolute suppression of the stem, as the terms acaulescent and 



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