224 The Botanical Gazette. {June, 
of these irregular cells is seemingly in nowise essentially dif- 
ferent either in time or character from that taking place in 
the mesophyll tissue of the lamina of the leaf. 
Purdue Universtty, Lafayette, Ind. 
EXPLANATION OF Pirates XIX anp XX. 
. <a Fi ‘ 
XX.—External and sectional views of petiole and pulvinus of mature 
i epidermis; 4, collen- 
m 
ature pulvinus. g. 4. ns, 
Trans. section of petiole immediately below the base of the pulvinus.— 
. Trans. sections approximately 1™™ apart, from lower to upper é d 
of upper pulvinus.—Fig. 12, Median dorsiventral long. section of mature upper 
us, 
