262 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



length of the normal, the epidermal cells of which, had a length 

 about four times the normal, affording an additional illustration 

 of the fact that the dimensions of the epidermal elements are not 

 governed by the amount of abnormal elongation of organs grown in 

 darkness. The laminae remained smaller than the normal, and did 

 not unfold from the rolled position of the earlier stages, and were 

 furnished with a small number of functional stomata. 



Sarracenia offers an example of a peculiar highly specialized leaf, 

 in which the laminar tract has been converted into the walls of an 

 ascidium. This receptacle is held in an upright position, and receives 

 decaying organic matter, which is absorbed in greater or less quan- 

 tity by the walls of the pitcher or ascidium. It is remarkable that 

 such leaves should show a reaction in darkness generally similar 

 to purely foliar leaves, the basal petiolar portion being excessively 

 elongated, and the utricular structure failing to be differentiated in 

 fully etiolated organs (see Fig. 136). 



Afoserisfoctida has been seen to undergo such excessive elon- 

 gation of the basal portion of the sessile leaf, when grown in dark- 

 ness as to become distinctly petiolate, and the midrib of the pinnate 

 lamina also increased in length and carried the pinnae farther apart 

 than in the normal green leaf.^'^'' Beta vulgaris bears leaves which 

 must be classed as arising from underground stems. According to 

 Sachs ^^" these organs reach a comparatively large size with a laminar 

 portion of a length of 11 to 12 cm., and a width of 4 to 5 cm., with 

 the margins inrolled. The tardier growth of the laminar tissues set 

 up a tension with the actively elongating midrib in such manner that 

 the latter was held in a curved position. 



It is to be seen therefore, that dicotyledonous leaves arising from 

 underground organs agree in failing to produce laminae of normal 

 structure and size, although some forms succeed in making an ex- 

 tended laminae, with a superficial extension approximately equal to 

 the normal. In no instance, however, is mesophyll full}' differenti- 

 ated. Stomata are formed which are generally smaller than the 

 normal organs, and not so many prestomatal elements are carried 

 forward to the advanced stage of development as in green leaves. 

 With but few exceptions the petioles and midribs are excessively 



"^Goebel, K. Organographie der Pflanzen. Part II., p. 499. 1898. 

 ^^^ Sachs. Ueber den Einfluss des TagesHchts auf Neubildung und Entfaltung 

 verschiedener Pflanzenorgane. Bot. Zeitung, 21 ; Beilage, p. 31. 1863. 



