HYPERTROPHIED LEAVES. 61 



trophy of the scales. The latter are thus shown to be reduced 

 leaves. They are to be compared to similar structures found on 

 shoots of certain other species of which Piniis rigida is an ex- 

 ample. These species are those which readily produce sprouts 

 from the stump. They may further be compared to the scat- 

 tered leaves occurring occasionally upon Larix, 



The structure of these abnormal leaves is not identical with 

 that of the true primary leaves — those produced on the seed- 

 ling on the stem immediately above the cotyledons. While not 

 so primitive as these primary leaves the)' may be compared more 

 properly to the Pseitdotsiiga type. 



The abnormal leaves described are ata\'istic, and the twigs 

 bearing them may be compared to a permanent condition such 

 as obtained in the Leptostrobi of the Potomac, a condition which 

 probably obtained also in those forms from the Jura of eastern 

 Siberia described by Heer. Leptostrobtts may safely be regarded 

 as in the ancestral line of the Pines. Laricopsis probably stands 

 in the same relation to Larix. 



Little can be said in regard to the causes beyond that over 

 nutrition plays no small part in the change. This suggests, at 

 least, that reduced nutrition may have been one of the more 

 important causes resulting in the evolution of the fasciculated 

 condition in Piniis and Larix. 



I wish here to acknowledge the kindness of Dr. Arthur 

 Hollick in indicating to me literature bearing on the fossil 

 conifers. 



