PLATE XXIII 



Malformed blossoms of tobacco {Nicotiana tabacum) caused by the mosaic disease, 

 which is often responsible for the various abnormalities shown. The corolla may 

 show mottling only, or it may develop very imperfectly, produciag various degrees 

 of catacorolla, fasciation, etc. In some instances the corolla fails to develop entirely. 

 The plants producing these acquired abnormalities as a result of the mosaic disease 

 have been studied as to their inheritance, but the descendants were healthy and their 

 blossoms normal . A common cause of sterility is the failure of successful pollination 

 of the stigma, owing to the abnormal displacement of pistil and stamens. Hand pol- 

 lination of such blossoms has often given capsules containing an abundance of fertile 

 seed. Blossoms as poorly developed as A, D, and H are usually incapable of producing 

 seed. The anthers, however, sometimes contain functioning pollen which may pro- 

 duce fertilization of the ovules when transferred to the pistils of healthy blossoms. 

 Blossoms E, F, G, I, J, K, and L usually produce seed if hand pollination is practiced. 



(256) 



