CHAP. XIV.] STONEWORTS. 431 



structure is continued from the cortical layer, across the 

 stem, at each node. The stem therefore consists of a series 

 of long, axial cells, contained in as many closed chambers 

 formed by the small cortical cells. The nodes are the mul- 

 ticellular partitions between these chambers. The branches 

 are altogether similar in structure to the main stem. The 

 leaves are also similar to the stem, so far as they consist of 

 axial and cortical cells, but they differ in the form and 

 proportions of these cells, as well as in the fact that the 

 summit, or free end, of the leaf is always a much-elongated 

 pointed cell. The most important distinction, however, 

 consists in the fact that the growth of the leaves is limited 

 while that of the axis is unlimited. The branches spring 

 from the acute angle between the stem and the leaf, which 

 is termed the axil of the leaf; and, in the same position, 

 at the fruiting season of the plant are found the repro- 

 ductive organs. These are of two kinds, the one large 

 and oval, the oogonia, the other smaller and globular, the 

 antheridia. Both, when ripe, have an orange-red colour, 

 and are seated upon a short stalk. 



If a growing plant be watched, it will be found that it con- 

 stantly increases in length in two ways. New nodes, inter- 

 nodes, and whorls of appendages are constantly becoming 

 obvious at the base of the terminal bud; and these append- 

 ages increase in size and become more and more widely 

 separated, until they are as large and as far apart as in the 

 oldest parts of the plant. The appendages at first consist 

 exclusively of leaves and root-filaments (rhizotds), and it is 

 only when these have attained their full size, that branches, 

 oogonia and antheridia are developed in their axils. 

 Sometimes rounded cellular masses appear in the axils of 

 the leaves, and, becoming detached, grow into new plants. 

 These are comparable to the bulbs of higher plants. 



