616 BOWMAN— ECOLOGY AND 



layers as a light screen will be considered in the physiology. On 

 account of the development of the hypodermis, the palisade lies 

 deep in the mesophyll, in fact almost in the middle of the leaf. 

 There are usually three layers of very narrow elongated palisade 

 cells. Interspersed among them are many branched and often much 

 twisted trichoblasts. These branches ramify about in intercellular 

 spaces and push the cells aside as they grow. The spongy tissue of 

 the leaf is rather loose and is composed of cells varying a great deal 

 in size. Some are large and contain tannin and others contain only 

 a thick mucilaginous protoplasm. Large spherical, many pointed 

 crystals of calcium oxalate fill up cells scattered in the spongy tissue, 

 as well as the water hypodermis (see Fig. 4, PI. VII). Warming 

 thinks the shining, thick epidermis of the leaves helps to reflect the 

 intense light and doubtless this is true and, as will be shown in the 

 physiology, this reflection serves an important service. 



On the under surface of the leaves are many small black specks, 

 which Warming regarded as the opening of glands located deep 

 within the spongy tissue. These were filled with a secretion which 

 looked brown in the material he examined, i. c, material pickled 

 in alcohol. It has now been shown that these tiny specks are not 

 glands, or glandular hairs, or disks, but really small bodies of cork 

 which are formed from the epidermal cells. 



The Flower. 



The inflorescence has already been described as usually di- 

 or trichsesial cymes, and its relation to the axis and the bracts has 

 been well described by other authors. The four stift" woody sepals 

 which persist and grow in size as the fruit develops are heavily 

 impregnated with stone-cells or trichoblasts. In the lower part of 

 the receptacle below the junction of the sepals and the ovary, i. e., 

 just beneath the ovules, there is a large mass of very loose tissue, 

 which Griffith'^ noted in his early papers on the species. This tissue 

 has very large intercellular spaces to permit the rapid growth of 

 the embryo to take place without unduly crushing the cells of the 

 fruit. The four petals placed alternately with the sepals are early 

 deciduous. They, as well as the sepals, are valvate and on their 



'•^ Griffith, W., Trans, of the Med. and Phys. Soc. of Calcutta. 



