248 Apical Gorwth in the Genus Trentepohlia. 
T. phyllophila W. & G. S. West. The lamellae of the cell-walls 
are practically parallel, and for the most part extend round the free 
end of the apical cell. Apical caps not discovered. 
T. calamicola (Zeller) De Toni. No definite results were 
obtained by the examination of this species, the specimens of which 
were preserved in alcohol. The whole exterior of filaments and 
branches appeared to be encased in a thin sheath of brown substance 
which entirely resisted the action of reagents, even of concentrated 
sulphuric acid. Both filaments and branches are frequently united 
into a sort of meshwork by this resistant substance. (A similar 
outer covering of resistant material was also present in a larger, 
but undetermined, species from Ceylon). 
Summary. 
In the genus Trentepohlia the cell-walls are lamellose and the 
lamella consist of cellulose. 
In some species the lamella are approximately parallel, and 
the growth of the apical cell takes place by the proportionate 
distention and permanent increase in area of all these layers. 
In other species the lamella diverge upwardly and outwardly, 
and the growth of the apical cell takes place by the distention of 
only the newly-formed layers, the older layers being burst through. 
In one species (7\ Montis-Tabulce var. ceylanica) the extreme 
case is reached where all the layers of theT cell-wall are burst 
through at the apex by the extension of the last-formed lamella. 
In many species of the genus, apical caps of pectose are 
secreted at the free end of the apical cell. These caps vary in the 
extent of their development. They are for the most part absent in 
species in which the lamellae of the cell-wall are parallel, and in 
which the wall at the free extremity of the apical cell is of approxi¬ 
mately the same thickness as the rest of the cell-wall. They are, 
however, developed in a varying degree in those species in which the 
lamellae of the cell-walls are divergent. The fewer the lamellae 
at the growing extremity of the apical cell and the more complete 
is the development of the apical cap. 
Species of Trentepohlia grow only in a damp atmosphere, and 
the structure of the apical cell in many species is such that its thin 
extremity requires efficient protection during those periods when 
the humidity of the atmosphere is below the normal. This 
protection is afforded by the apical cap, which may therefore be 
regarded as protective in function. 
