LOVEJOY : ANATOMY OF G^RTNERIA. 281 



Water-storage Tissues. 



That the leaf of Gsertncria deltoidea is unusually well sup- 

 plied with water-storage tissue is shown by the fact that the 

 ultimate ends of the veins vary from .2 to .025 mm. in distance 

 apart from each other. A portion of the water used by the 

 leaf passes straightway into the palisade cells from water 

 tubes ; other portions pass into large cells making up that part 

 of the venation system used primarily in water storage. As 

 there are chloroplasts found in these cells, it would appear that 

 they function to some degree in photosynthesis as well as in 

 water storage. In figure 43 are shown palisade cells lying in 

 connection with water-storage parenchyma cells, thus directly 

 gaining access to the stored water. In connection with the 

 venation system of the leaf are also other water-storage cells, 

 which, unlike the cells just mentioned, have highly thickened 

 and plain-pitted walls, and in most cases these lie near the 

 edge of the leaf at the ultimate ends of the vein branches there. 



In studying the venation system of the leaf, it was found 

 advantageous to put the leaf sections, etc., through a clearing 

 process. This clearing of cells was very satisfactorily accom- 

 plished by using Mr. L. M. Peace's method of cell clearing and 

 bleaching, which is described in Plant World, vol. 13, April, 

 1910. 



By this method whole leaves were successfully cleared of cell 

 contents, and then, when put in an alcoholic solution of safra- 

 nin for a period of twenty-four hours, they showed with re- 

 markable clearness the whole system of leaf venation, the 

 tracheal elements being the only part of the leaf to take on, to 

 any degree, the safranin stain. As shown in figure 30, the leaf 

 of Giert7ieria has a prominent midrib extending the full length 

 of the leaf, with two lesser lateral longitudinal veins which are 

 distinct for only a portion of the distance from the base to the 

 tip of the leaf. From these extend branches throughout the 

 leaf in every direction, the distances between the ultimate ends 

 of which vary from .2 mm. to .025 mm. 



Many of the veins end in the midst of a bundle of water- 

 storage parenchyma cells, as described above. In a cross sec- 

 tion through the petiole of the leaf near its base were found 

 ninety-four tracheal tubes, the average diameter of which was 

 .0055 mm. 



