XVIII THE CRATERS OF THE RIFT VALLEY 24 I 
perhaps fifteen or twenty years. Once a lobelia has 
reached the stage of producing a flower-spike and burst¬ 
ing into blossom, it has reached the end of its life. It may 
take twelve months for the spike to finish blossoming; 
then the whole plant withers and dries up, and probably 
stands for several years before it falls and is swallowed 
up by the moss. In L. Stuhlmanni the leaves as they 
die fall off, leaving the stem bare except for green leaves. 
The flower-column of a Tree-lobelia, 
L. Telekei, Kenia ; real size. 
The blossoms are shown open anil closed. The 
sepals are bright green ; the petals, violet. 
Ill L.- Deckenii none of the leaves fall off and the stem 
is entirely concealed by them, from the ground up to 
the spike, wTich has a much greater circumference than 
ill other lobelia. This species without its flower-stalk 
often appears as a rosette of leaves squat on the 
ground. 
In L. Wollastoni some leaves fall off and others 
remain hanging, so it usually has a portion of the stem 
exposed. These differences in the relation of the dead 
R 
