THE LtiAF. 



233 



that spiral pliyllotaxis is primitive, Celakovsky is 

 probably correct in his view that the terminal cotyledon 

 of Monocotyledons is also primitive, and that the two 

 cotyledons of Dicotyledons have been derived therefrom 

 by splitting, which is in direct opposition to the pre- 

 vailing modern view which regards the Monocotyle- 

 donous type as dne to reduction from the Dicotyledonous 

 one. If the modern prevalent view is correct we ought 

 surely to occasionally find the single cotyledon of 

 Monocotyledons abnormally forking or else replaced 

 by a pair of cotyledons ; but such phenomena are 

 entirely unknown. We have in the short-shoot of Pinus 

 mnnophyIJa a perfectly parallel case, in which the single 

 terminal leaf results from the suppression of one of the 

 members of the original pair; yet here the reappear- 

 ance of the missing leaf is not at all an infrequent 

 phenomenon. Why does the same thing never occur 

 in the Monocotyledonous seedling ? 



On the other hand, the view that the Dicotyledonous 

 condition is secondary and derived is supported by 

 the fact that single cotyledons, due to fusion of two, 

 occur very commonly as an abnormality in Dicoty- 

 ledons. This may be regarded as a reversion, and 

 this explanation, in the absence of any other, must 

 hold the field. 



The reason why the Dicotyledonous seedling offers 

 such frequent " sports " as regards the number of the 

 cotyledons maybe attributed to the fact that the Dicoty- 

 ledonous type of seedling is a comparatively recent 

 variation from the primitive Monocotyledonous type ; 

 and the staid and invariable character of the latter 

 is thus explained. 



Where a single cotyledon is present in an abnormal 

 seedling, it is invariably followed by a single foliage- 

 leaf, and in plants which normally have opposite- 

 decussate pliyllotaxis this is replaced by the spiral 

 type, a fact which again betrays the powerful influence 

 of the cotyledonary node in regulating the leaf-arrange- 

 ment on the plumular shoot. This phenomenon also 



