n.] 



NAIADES. 



219 



OBSERVE the sheathing axillary stipules of Pondweed : 

 the tubular pollen-grains, destitute of an outer coat 

 (extine), of Zostera, a plant with narrow, ribbon-like 

 leaves, growing in the sea near low-water mark : the 

 exalbuminous seeds of the Family. 



It is remarkable that most of the Orders of Monoco- 

 tyledons of aquatic habit are destitute of albumen in their 

 seeds. 



Allied to the Pondweeds is the rare Lattice-leaf (Ouvi- 

 randra fenestralis) of Madagascar, the cellular tissue of 

 the leaves of which is so reduced that open spaces occur 

 between the veins, which form a delicate network 

 resembling a " skeleton-leaf." 



From the extreme importance to mankind, the number of 

 species, and majestic aspect of the Palms, a short notice of the 

 Order to which they belong (Palmacese) is needful here, 

 although none occur in Britain, and but a single species, the 

 Dwarf Fan Palm Chamtzrops hu mills), is native in Europe. 



Palms are perennial Monocotyledons, either arborescent, 

 rising sometimes to a height of 100 or 200 feet, or acaulescent 

 (having no apparent stem), with a short or prostrate rhizome. 

 The stem is rarely branched, growing only by its terminal bud. 

 A cross -section of the stem is well adapted to show the irregular 

 arrangement of the isolated vascular bundles characteristic of 

 Monocotyledons. The leaves form an immense crown, termi- 

 nating the stem, and are often, singly, many feet in length. They 

 are usually either of the radiate- or penni-veined type, though 

 some are intermediate between the two forms. The flowers are 



