and Growth of Monocotyledons. 187 



greater consistence which the older parts of the stems of Palms 

 acquire is to be regarded as arising from causes similar to those 

 producing the peculiar characters of the heart-wood of Dicoty- 

 ledons. 



DESCRIPTION OF THE PLATES. 



Plate IX. 



Fig. 1. A branching rhizome of Sparganium ramosum, exhibiting the nodes, 

 a, and the internodes, b ; in the latter the fibro-vascular bundles 

 take straight and parallel courses. 



Fig. 2. Half of a vertical section through a terminal bud, showing the re- 

 lative positions of the developing bundles, a, the central paren- 

 chymatous region, in which the bundles lie ; b, the line where the 

 fibrous layer is formed by the lower extremities of the bundles ; c, 

 the cortical region in which lie the liber (?) bundles ; d, the punc- 

 tum vegetationis. 



Fig. 3. A similar section ; the references are the same ; e e are nascent 

 roots (figs. 2 and 3 are magnified six diameters). 



Fig. 4. A portion of the cortical region with liber (?) fibres continued into 

 the leaves. 



Fig. 5. Vertical section of a full-grown node (like a of fig. 1), prepared by 

 maceration, so as to exhibit the fibro-vascular bundles in situ, a, 

 the bundles ; b b, axillary branches forming the internodial por- 

 tions (like b in fig, 1) ; c, the cortical region, now a mass of fibres ; 

 d, the fibrous layer, which presents several layers of densely inter- 

 woven fibres derived from the lower extremities of the bundles of 

 the central region. 



Fig. 6. Transverse section of an internode (b in fig. 1). a, the central re- 

 gion ; b, the fibrous layer ; c, the cortical region, here very much 

 developed. 



Fig. 7. Vertical section of the same, a, b, c, same references ; d, a root, the 

 central fibro-vascular bundle of which is seen arising from the 

 fibrous layer. The root breaks down the substance of the cortical 

 region when making its way out. The fibro-vascular bundles of 

 the stem are parallel here, and the slender liber (?) bundles are 

 shown in the cortical region c. 



Plate X. 



Fig. 1. Highly magnified vertical section of a bud. a, the nascent fibro- 

 vascular bundles. 



Fig. 2. Transverse section of a portion of an internode. a, the central re- 

 gion ; c, the fibrous layer giving off" the vessels to the root # ; d, the 

 cortical region ; e, liber (?) bundles ; /, epidermis (enlarged about 

 five times). 



Fig. 3. Part of the same highly magnified, a, the parenchyma of the central 

 region of the stem gradually becoming converted into ligneous 

 cells as it passes into the centre, b, of the fibro-vascular bundle of 

 the root ; c, the ducts which are given off from the fibrous layer to 

 form the vessels of the root ; d, the cortical parenchyma of the stem. 



Fig. 4. Magnified section of the cortical region, showing the large inter- 

 cellular spaces (the cells of this tissue are extremely irregular in 

 form, and contain no starch granules), e, a liber (?) bundle. 



