410 RUSSELL— A COMPARATIVE STUDY OF 



Leaflets were imbedded in paraffin and sectioned. These showed a 

 characteristic umbrophytic structure. In transverse section there 

 appeared: — An upper epidermis of rounded cells, not thickened (Fig. 6), 

 containing stomata. Below the epidermis is a layer of loose palisade 

 tissue, rich in chlorophyll, with many open intercellular spaces lying 

 below the stomata. Below the palisade tissue is a narrow zone of meso- 

 phyll tissue containing the bundles. There are, in transverse section of a 

 leaflet, a stronger midrib, two lateral strong veins, and two intermediate 

 smaller veins. The vascular bundles are poorly developed, showing 

 merely a few xylem and phloem cells. The lower epidermis is identical 

 with the upper, excepting for the presence of more stomata. The veining 

 in a leaflet consists of a midrib, branching at the base into two lateral 

 branches running along the margin of the leaflet, and uniting with the 

 midrib at the tip. From the margin lesser veins rim toward the middle 

 of the leaflet. A longitudinal section (Fig. 7) through the median part 

 of a leaflet shows at the tip a single hydathode. From the end of the 

 united bundles at the tip a mass of parenchymatous tissue spreads out 

 in a fan-shaped mass. These cells are filled with a denser protoplasm 

 than the surrounding cells. This is the epithem tissue of the hydathode. 

 It lies immediately below a circular area of epidermal cells at the tip of 

 the leaflet. The cells of this area differ from the ordinary epidermal 

 cells in that they are oblong in shape and have smooth, straight walls. 

 Stomata are more numerous than in the epidermis outside this region 

 and are of smaller size (Fig. 8 and 9). The guard cells of these stomata 

 are always open. The stomata themselves are more nearly spherical 

 in outline than the normal stomata, which are elliptical in shape, and 

 usually have their guard cells closed. 



The water stomatic area at the tip in the older leaflets undergoes a 

 breaking down in the epidermal cells, forming in this way a water pore 

 (Fig. 7). 



In both Floerkea and Limnanthes the leaves are glabrous. In Limnan- 

 thes, however, there are present tannin containing cells on the under 

 surface of the leaf. They are long slender cells, running parallel to the 

 axis of the leaflet. Sometimes they are present on the outer face of the 

 sepals (Fig. 13). These are mentioned by Solereder (25). They give a 

 positive reaction for tannin upon the application of ferric chloride. 

 There are no tannin cells present in Floerkea proserpinacoides. 



Flower 



The flowers of F. proserpinacoides are solitary axillary. All the leaves, 

 except the first foliage leaf, bear a flower in the axil. 



