345 
Anatomy of Spartina Townsendii . 
large clear cells (Fig. 4, 2, w) y from their watery contents and proximity to 
the bundles, may be regarded as a kind of transfusion-tissue, or water- 
storage system. Two or three rows of similar large cells extend from this 
vascular sheath and unite with the subepidermal stereome. These at first 
also contain chloroplasts, which gradually diminish or even disappear finally. 
Ultimately these cells have a large water-content. They compose the main 
part of the mesophyll bridges supporting the bundles, and by their turgidity, 
combined with the sclerenchyma strands, form girders strong enough to 
keep the leaf erect even when unrolled. 
The chlorenchyma consists of irregular stellar cells, curiously elongated 
like a palisade layer, with radiating lateral arms and large intercellular 
Fig. 5. 1. Longitudinal section through junction of leaf-blade and sheath: (I) parenchyma 
cushion ; (II) thickened pad of articulation with split (sp) ; (III and III') sclerenchyma sheath 
surrounding reduced vascular bundle ; (/) ligule ; (sc) sclerenchyma ; (vb) vascular bundle. 
2. Enlargement of regions (I) and (III), showing type and distribution of supporting tissue, and 
pitting. The large colourless soft-walled cells under the convex thin-walled epidermis represents 
the active part of the pulvinus. 
spaces, as in Fig. 4, 2, ch. It extends along the furrow to a little way 
below the bottom of the groove, between the water-storage ring and a short 
median line of two or three circular cells (Fig. 4, 2 , c), whose walls approach 
collenchyma in structure, in this respect corresponding to inner walls of the 
motor-cells below whose median line they lie. The partition cells probably 
both help to strengthen the hinge arrangement and aid the motor-cells to 
absorb and to give up water. They terminate on the air-passages which 
run between the bundles through sheath and blade. 
The air-passages arise from blocks of rounded cells with few or no 
chloroplasts. The cells become stellate and finally collapse, forming the 
lacunae (Fig. 4, 2, ap ), which are interrupted by transverse diaphragms. 
