56 BOTANICAL GAZETTE [july 



a form without the widely spreading base, showing ascending 

 margins, and with but an indication of the spreading basilar 

 extensions or lobes which characterize the mature leaves. 



Liriophylhtm Beckzvithii is either an abnormal form of L. popu- 

 loides, or a further extension and more pronounced development 

 of its salient characters. Of rare occurrence and large size, it 

 may simply represent a leaf of L^ populoides of extraordinary 

 size and more extensive lobation, induced by favorable conditions 

 of growth, just as we find extraordinarily developed leaves of 

 large size and extensive lobation on especially vigorous shoots 

 from saplings of L. Ttilipifera. 



Sterile soil, lack of humidity, or some similar hard condition 

 may account for the development of the Liriophj^llum type of 

 leaf. The following facts would seem to imply this : In L. Tulip- 

 iferUy the leaves on the same twigs as the flowers tend to an 

 abbreviated blade. Again, by cutting off the shoots of the year, 

 and forcing next yearns buds to take their places, we obtain 

 leaves similar to the above. All of these forms approximate 

 Liriophyllum, and hint at its probable mode of origin. That the 

 peculiar ascending primaries offer no objection to this theory is 

 well shown in several small specimens of Z. Tulipifera leaves in 

 my collection, with a cleft apex and opposite ascending veins. 

 It would require only the slowly increasing development of an 

 opposite- veined and cleft-tip form like this to become the 

 opposite-veined, deeply cleft Liriophyllum. 



As the Dakota time progressed, Liriodendron, fostered by 

 the humid and warm Cretaceous climate, developed rapidly, the 

 leaves increasing greatly in size, and with this went increased 

 lobation, the tendency being for those portions of the leaf blade 

 at the terminals of the secondary veins to increase at the expense 

 of the rest of the blade. These lobes are obtuse where a full or 

 an extra supply of nourishment is obtained, and acute where 

 there is any diminution of the supply. That the congenial 

 warmth, humidity, and rich soil of this period were the primary 

 factors in the great variation and development of the Lirioden- 

 drons is undoubtedly the case; for in modern tulip trees those 



