Berry: Origin of Stipules in Liriodendron 497 



tudinal, the usual manner ; the union of the wings with the petiole 



forms an angle of about 90 . 



On Plate 42, Fig. 9, we have a slightly more advanced 

 stage than that shown on Plate 42, Fig. 2 ; the leaf shows traces 

 of lobation and the wings are more like stipules both in shape and 

 venation, and are more separated from the petiole, the angle 

 formed by the union with the latter being about 45 °. 



In the form shown on Plate 41, Fig. 6, we have the closely 

 succeeding stage in the series. The wings are very broad, being 

 fully as wide as the blade proper. This form resembles Plate 41, 

 Fig. 5, in the outline of its blade, while the wings are but slightly 

 removed from the preceding, being a trifle freer from the petiole. 



We place as the next stage in the series Fig. 5 on plate 42, 

 for although the petiole is much lengthened and the wings are con- 

 siderably reduced, still they are attached to the petiole for over 

 half of their length. Fig. 8, plate 41 , closely follows the preced- 

 ing. While the leaf-blade is of a different shape, the petiole is of 

 similar length and its appendages are similar in size and form ; the 

 only difference being that they are free for more than half their 

 length, approaching the next stage in their degree of attachment. 



On plate 41, Fig. 7, we have a somewhat more advanced 

 stage ; the blade proper is orbicular in general outline with a slightly 

 emarginate apex, exactly similar to dozens of leaves which may be 

 found on young shoots ; the distance from the blade to the wings 

 is comparatively great (one and one-quarter inches), almost the 

 same as the length of the blade ; wings are attached to the petiole 

 by their bases only and are widely divergent ; they are somewhat 

 larger than in the preceding form. From this to the regular mod- 

 ern stipulate form, it is but a step, which interval we bridge over 

 with the form shown on Plate 41, Fig. 3. At first glance the 

 stipules appear entirely free, but closer examination shows that 

 they still retain their connection with the petiole by means of a 

 small triangle of connective tissue (shown enlarged at Fig. 4, 

 Plate 41). 



The modern form of stipules is shown in Figs. 3, and 8, on 

 Plate 42, Fig. 3 being the small form the leaf assumes on young 

 shoots and saplings, and Fig. 8 that of the normal modern form 

 of leaf. 



