Notes on Floricleze. By George Massee. 569 



the basal cells of the branches, and not having yet reached the nest 

 whorl of branches below, between which they pass in their down- 

 ward growth. In some species these corticating branches them- 

 selves branch, the ultimate branches developing at right angles to 

 the stem, and presenting the appearance of hairs. In the genus 

 Crouania, this mode of cortication is yet more complex. A third, 

 and by far the most universal method of cortication results from 

 branches which spring from axial cells in a scattered or whorled 

 manner, becoming densely corymbose and of equal length, the cells 

 decreasing in size from the base to the tips of the branches. The 

 cells of adjoining branches are agglutinated together, so that a 

 dense continuous pseudo-parenchymatous cortex of small closely- 

 packed cells results, the interior of the thallus consisting of com- 

 paratively few large cells. This type of cortication is well shown 

 in the genera Caulocanthus, Halymenia, and Gloiosiphonia. 



The growth in diameter of cells is generally uniform when 

 free from pressure and not giving origin to lateral branches, and 

 the transverse section circular, while the zone of growth that adds 

 to the length of the cell may be most vigorous near the posterior 

 end, as in the genus Ceramiiim, where the axial cells when young 

 are thin discs, from the anterior margin of which are cut off the 

 cortical cells, the naked portion below increasing much in length, 

 while no increase in the length of the cell takes place anterior to 

 the origin of the cortical cells. In the genus Polysiplionia growth 

 is uniform or nearly so throughout the entire length of the cell, 

 which is also disc-shaped at first, and soon segmented into an axial 

 surrounded by cortical or pericentral cells, the protoplasts being 

 connected by well-defined threads of protoplasm. After having 

 attained their full size the connecting threads are seen to occupy 

 the central portion of the length of the cells, showing an equal 

 rate of growth in length anterior and posterior to what was origi- 

 nally the middle of the length of the cell. The first differentiation 

 observable in the cellulose of external cells is the formation of a 

 cuticle, which in the fully developed plant can be shown to exist as 

 a continuous pellicle investing every part. It resists for a long 

 time the action of acids and alkalies, and when treated with chlor- 

 iodide of zinc or sulphuric acid and iodine, assumes a brown or 

 yellowish colour. Surface growth, or increase in size of the cell- 

 wall, appears to be due to intussusception, as micro-chemical tests 

 show a uniformity of composition throughout ; but the thickening 

 of the cell- wall, so conspicuous in many seaweeds, is clearly due to 

 apposition, the cell-wall when young changing to a bright blue 

 when treated with sulphuric acid and iodine, but as the wall 

 increases in thickness the innermost and last added portion alone 

 shows this reaction, the outer portion becoming brow r n or reddish, 

 gradually passing into blue as it approaches the inside. Worms- 



