the Secretory Tissties of the Marattiaceae. 
413 
The arrangement of the small cells constituting such a group is usually 
very irregular (Text-figs. 3-4 ; Figs. 6 and 12). 
Most botanists have agreed as to the earlier stages in the development 
of the mucilage-canals, but much confusion has arisen in the past as a 
result of the difficulty of correctly interpreting the subsequent stages. 
Whereas some (e. g. Frank, Brebner, Lutz) have maintained that 
the cavity of the duct originates by the splitting apart of the walls of these 
small cells, which persist as a definite epithelium lining the intercellular 
space into which they actively secrete mucilage, others (e. g. Kuhn, Farmer 
and Hill, Campbell) have ascribed a lysigenous origin to the canals and have 
asserted that the cavity is formed by the collapse and disorganization 
of these groups of cells, which become converted into mucilage. 
Text-fig. 6. 
Text-fig. 5. 
Early stages in development of mucilage-canals in the stem of Danciea alata , Sm. x 350. 
The shaded areas represent protoplasm in process of mucilaginous degeneration. 
My own observations, which extend over five genera and many 
species, for the most part confirm the explanation given by the latter 
group of botanists. 
The cytoplasm of certain cells of the group undergoes local mucilagi¬ 
nous degeneration (Text-figs. 1-5 ; Figs. 6 and 11-14). Kleinenberg’s 
haematoxylin was found most satisfactory for demonstrating the changes 
which take place in the cytoplasm, since it clearly differentiates between the 
unaltered cytoplasm and that which is undergoing mucilaginous degenera¬ 
tion. This process usually begins near the common point of contact of the 
cells, and gradually extends through the cytoplasm until finally the entire 
contents of the cell, including the nucleus, are involved in the change. The 
cell-contents meanwhile undergo a marked contraction and frequently come 
away from the cell-wall (Figs. 6 and 13). 
In this way a condition is attained which might easily be mistaken for 
a splitting apart of the cell-wall, especially when it is remembered that 
