MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 169 



whether it was the consequence of application of water about the 

 hour in question, after which elongation increased. (Fig. 128.) 



The composition of etiolated leaves of rhubarb has been the sub- 

 ject of tnany studies and tests on the part of practical investigators, 

 and the cultivation of this plant in darkened cellars, and in total dark- 

 ness is an industry followed by many gardeners. This method of 

 cultivation appears to have been hit upon by Knight. A recent manual 

 gives the details of management of these plants in darkness.'^* 



Rhus sp. (native shrub). 



A root of Rhus carried into the dark room in March with a clump 

 of soil adherent had developed a shoot 35 cm. long with seventeen 

 rudimentary leaves by May i, the lower eight of which had fallen 

 off. The angular outline of the normal stems was preserved, and a 

 number of lenticels were formed near the base of the shoot. The 

 pith was composed of uniformly thin-walled cells with large intercel- 

 lular spaces. A cambium layer could not be made out, but some 

 bundles which from their position must have been of secondary for- 

 mation were to be seen. The cortex was very thin-walled and no 

 thickening of the subepidermal tissues was seen. The epidermis was 

 free from stomata, but bore numerous pointed and glandular hairs. 

 The sections assumed a milky appearance on being placed in water. 



The leaves attained a total length of over a centimeter and were 

 curved downward. The two basal pairs of pinnae were extended 

 but had a total length of only a few mm. The leaves were densely 

 hairy, showing both forms of trichomes as noted below. No stomata 

 were formed, which rs correlated with the brief existence of the 

 shoots which soon die in darkness. 



Ricinus communis L. 

 Seeds placed in dark chamber germinated and produced hypo- 

 cotyledonary stems 30 cm. in length, which were weakly erect. The 

 cotyledonary stalks were 2 to 3 cm. long. The cotyledons were not 

 freed from the endosperm in any instance, and made no growth, 

 soon falling off, exposing the plumule. The first pair of leaves 

 attained a length of about 8 mm. If the endosperm were removed 

 the cotyledonary stalks curved downward after the customary move- 



•3* Knight, T. A. On a method of forcing rhubarb in pots. Trans. Hort. Soc. 

 Lond. 3 : 154. 1820. 



Morse, J. E. The New Rhubarb Culture. New York, 1901. 



