80 THE ROYAL SOCIETY OF CANADA 



Sometimes an extensive new growth or regeneration takes place, 

 resulting in a curious doubling or overlapping of lobes of injured leaves. 

 The power of the injured tissues to heal is also responsible for adhesions 

 between parts that lie folded together in the bud. These adhesions 

 are usually responsible for failure of normal expansion of the blade." 

 In the radiating scars one can recognize the "enations" which have 

 been above described, and it has been shown that these are not con- 

 nected with any such histolysis as Cook has referred to. The opinion 

 may be ventured therefore that he was really observing two pheno- 

 mena, one which is due to abnormal development, and one due to 

 secondary destruction of tissues, both of which may be caused by the 

 same set of conditions. My own observations made on seedlings in 

 the glass-house (when tomosis was absent) and in the field, have led 

 me to this view. 



Summary. 



1. Under special conditions, consisting in prolonged period of 

 physiological drought followed by temperatures and water supply 

 favourable for growth, the leaves of the cotton {Gossypium herhaceum) 

 are induced to form ascidia. Similar conditions have been observed 

 to induce fasciations in many species, while ascidia seem to appear 

 more frequently under conditions of cultivation, both under glass 

 and in the open. 



2. Such conditions appear to procure the above result by the 

 mechanical pressures set up in the growing buds by the resistance 

 offered by the indurated outer regions to the exuberantly growing 

 parts within. 



3. The characters of the incompletely ascidiate leaves, consisting 

 in foldings, sinuses, concrescences, enations, support this inter- 

 pretation. 



4. The malformations in question are not identical with tomosis, 

 but may appear concurrently under the conditions described by O. 

 F. Cook. 



5. While these malformations, or rather the physiological con- 

 ditions producing them, are inherited in some species there is at the 

 present no further evidence that the same is true of the cotton plant 

 except that offered by the 'cluster' varieties, in which concrescences, 

 fasciations, and concomitant behaviours, are dominant. 



