PRATT: CYCLOLOMA ATRIPLICIFOLIUM. 105 



The water-storage tissue is made up of large cells centrally- 

 located and lying next the border parenchjTna adjacent to the 

 vascular elements ffigs. 72, d; 73, d; and 79, d). The vascular 

 elements of the leaf are imbedded in the mesophyll in closer prox- 

 imity to the lower than the upper epidermis (figs. 71, g; 72, g; and 

 73, g) . Under the upper epidermis of the leaf is a palisade 

 layer of mesophyll, and just below there is a layer of mesophyll 

 parenchjTna joining up with the water-storage tissue (figs. 70, V" 

 and m'", and 71, V" and m'"). A surface \iew of a bleached leaf 

 embracing the epidermal, the palisade and the vascular bundle 

 systems is shown in fig. 80. Between the water-storage tissue and 

 the lower epidermis is a layer of mesophyll two or three cells 

 deep (figs. 71, n'" and 72, n'"). The intercellular spaces in this 

 are too small and regular to form a typical spong>' tissue. The 

 mesophyll cells are shown in tangential section in fig. 81. A 

 typical spongy tissue has not been observed in any species of 

 the Chenopodieae, according to Solereder. 



In the main rib of the leaf collench\Tna cells join up the water- 

 storage tissue and cells of the lower and upper epidermis, as shown 

 in figs. 71, b, and 72, b, and the main rib projects out farther on 

 the under side of the leaf than on the upper, there being more 

 coUenchyma in the under side of the main rib. Collenchyina 

 serves as a strengthening tissue in the tip of the leaf and also in 

 the tip of each lobe of the leaf, as is shown in fig. 82. 



The venation of the leaf is mapped out in fig. 83, which is made 

 from a whole leaf bleached and cleared by the method of Peace 

 ('11). To hasten the removal of the abundant calcium oxalate 

 crystals, the leaves treated were left over night in 10 per cent 

 hydrochloric acid after being treated with 5 per cent potassium 

 hydroxide solution. The leaves were then stained with safranin 

 in a concentrated chloral hydrate solution; and the surplus stain 

 having been washed out in distilled water, the leaf was bleached 

 in chloral hydrate solution until just the vascular system retained 

 the red color. The leaf venation is very irregular and does not 

 form a close network. In each lobe of the leaf a main branch of 

 the vascular system finds its termination (fig. 83). 



The venation of the leaf ends blindly throughout the mesophyll 

 (fig. 84), except at the edge of the leaf, where the ultimate endings 

 are groups of tracheids extending out close to the epidermis 

 (fig. 85). The ultimate endings of the venation stand on an 

 average of .9 mm. apart in the greater part of the mesophyll of 

 the leaf, but the tracheid endings at the edge of the leaf stand 



