78 THE ROYAL SOCIETY OF CANADA 



Because the leaves of the cotton are not opposite and because of 

 their complex vernation, the effects of these mutual interferences are 

 not easy to follow. That the mutual relations of alternate leaves 

 produce similar results I am satisfied by observations on Jnglans 

 californica quercina, Fraxifius sp. etc., and there is evidence that the 

 same condition obtains in the ascidiate Cytisus Attleyanus} In 

 Scrophularia californica, which has opposite leaves, transverse xon- 

 strictions, apparently identical in origin with those shown in the 

 accompanying figure 3, frequently occur. 



That some such condition as the above is required to call out the 

 abnormal behaviour of which the formation of ascidia is the extreme 

 expression, seems to fiow from the fact that the cotton-plant can be 

 forced so to behave by means which can hardly be interpreted to work 

 otherwise. Furthermore, while it is proved that the tendency to 

 malformation is inherited,^ it requires certain external conditions to 

 insure their expression.^ The very various behaviour of the ascidiate 

 Fraxinus above mentioned, although the expression of an inheritance* 

 points to the same conclusion. Thus, the formation of deep wine- 

 glass shaped ascidia in the older, and shallow ascidia in the next, and 

 none at all in the youngest leaves,^ seems to point to gradual relief 

 from more or less severe pressures. Also the fasciation of petiolules 

 with the mid-rib, not infrequent, has a like implication. 



Concerning the mode of origin, it is pertinent to offer the following 

 comment. In the description of ascidia, "enations" and the like, 

 the term "fusion" is frequently used. That, however, fusion takes 

 place between two primarily separate leaves or parts is exceedingly 

 doubtful. Although a series, as above described, can be arranged, it 

 does not mean that there are corresponding stages in ontogenetic 

 development. A condition which we assume causes a transverse 

 fold, when more drastic causes two free margins and a continuous 

 gap between, cutting ofif a complete ascidium. But this gap does not 

 originate as a fold. Similarly, an "enation," morphologically the 



^DeVries.H. Sur la périodicité des anomalies, etc. Arch. Neerl. II. 3:371-413' 

 pi. 7, 8. 1900. 



2K. Gœbel, Organography, Vol. 1, p. 184. 



^Hus. H. Inheritance of Fasciations in Zea mays. Plant World. 14:88-96. 

 April, 1911; Worsdell, W. C. "Fasciation": Its meaning and Origin. New 

 Phytologist. 4:55-74. Feb. Mar. 1905. 



«Shull, I.e. 



^Ascidia in Trifolium repens, Tilia, and Saxifraga occur in the earliest formed 

 leaves, while in Ulmus campestris the opposite, namely in the strongest and, upper- 

 most leaves of the shoot (deVries, H. Mutations théorie, Vol. 1, p. 641). It is, 

 however, quite possible that the gradual cessation of growth can set up similar 

 conditions. 



