280 Transactions. 



The spongy tissue consists of very large, irregular, thin-walled cells 

 which are loosely arranged, so that there are large air-spaces. These 

 cells also contain numerous chloroplasts, which are, however, smaller than 

 in the palisade tissue. Just above the lower epidermis there is a single 

 layer of more closely arranged roundish cells with abundant large chloro- 

 plasts like those in the palisade tissue. 



Surrounding the vascular bundle there is a sheath of small, irregular, 

 thin-walled, colourless, parenchymatous cells. Between the sheath around 

 the midrib and the lower epidermis the cells are smaller, compactly 

 arranged, and contain fewer chloroplasts. The vascular bundle contains 

 only a small amount of lignified tissue. 



Stem, (fig. 2). — The epidermal cells are small and roundish, and have 

 their external walls somewhat thickened. There is a very thin cuticle. 

 Some of the epidermal cells are produced into hairs like those on the leaf. 

 The stomata are level with the surface ; the guard-cells have thickened 

 walls. 



Below the epidermis there is a layer of small round cells which have 

 thin walls and which contain numerous chloroplasts. Between this layer 

 of cells and the rest of the cortex there is in most parts a large air-space.. 

 Below the air-space the cortical cells vary considerably in size. The 

 fiist layer consists of roundish cells with fairly numerous chloroplasts ; 

 then the cells become much larger. They are more or less polygonal and 

 fairly compactly arranged, so that there are only small intercellular air- 

 spaces. These cells contain a few small chloroplasts ; these are found 

 near the corners where three cells meet. Just above the phloem the cells 

 are smaller. All the cortical cells have thin walls. 



The amount of phloem is small ; the sieve-tubes and the phloem- 

 parenchyma cells are of small diameter. 



The xylem forms a continuous band ; it consists chiefly of wood-fibres 

 with somewhat thickened walls, and also of a few vessels ol small diameter. 



The pith is wide and is solid ; just below the xylem the cells are 

 smaller, but as we pass inwards the cells get very large ; they have thin 

 walls, and are arranged so that there are small intercellular air-spaces. 



28. Euphrasia Monroi Hook. f. 



^Hahit. — The plant is a small perennial herb with stems erect or 

 decumbent below, 3-8 in. high, leafy above and sparingly branched. The 

 leaves are rather close-set, spreading, ^-^ in. long, obovate or obovate- 

 spathulate, obtuse, narrowed to the base but not evidently petiolate, 

 coriaceous, glabrous, and having one short obtuse tooth on each side. 



Anatomy. 



Leaf (figs. 3-6). — On examining the leaf one observes on both surfaces 

 some well-marked grooves. These are shown in figs. 3 and 4. These 

 grooves are dark brown in colour, and are much more numerous on the 

 lower than on the upper surface. On the upper surface there are only 

 two ; these pass from the midrib to the single tooth on each margin of 

 the leaf. On the undei surface there is a groove running almost round 

 the leaf close to the margin. This groove is somewhat irregular in outline ; 

 from it numerous other grooves branch off. Cheeseman ( Manual of the 

 N.Z. Flora, 1906, p. 554) in describing this plant does not mention these 

 grooves. When transverse sections are, taken of the leaf it is seen that 

 the grooves are lined with cells which are water-absorbing cells. 



