Miss G. Lister. 
1 5 
ON THE OCCURRENCE OF TKISTICHA A L TE RNIFOLIA , 
Tul., IN EGYPT. 
By Gulielma Lister. 
[With Figs. 1-3 on Plate I.] 
I N the early part of February, 1900, while passing in one of the 
native boats among the islands below the first cataract on 
the Nile, my attention was drawn to a brilliant crimson moss-like 
plant that was covering part of some of the rounded granite 
rocks projecting from the rushing water. On near approach, the 
plant was seen to be clothing the rocks for about a foot above 
water-level, and extending for a considerable depth below, covering 
altogether an area of about ten square yards; the upper part was 
dry and knotted into tufts (of a drab or greenish colour, while where 
it was wet and fresh the colour was red. It seemed probable from 
its manner of growth that the plant belonged to the Podostemacece , 
and a fair quantity was scraped from the rocks, the swiftness of the 
current making the process not easy; search was made for flower 
or fruit without success. 
On our return to England the plant was referred to Professor 
Warming, of Copenhagen, who identified it as being in all probability 
the var. pulchella Warmg. of Tristicha altcrmfolia Tul. ; he has since 
published a description and figure of this gathering in the sixth of 
his Memoirs on the Podostemaceas, 1 and mentions that this is the 
first record of the order from Egypt. As his full account is in 
the Danish language, I venture to give here a further description. 
The Podostemaceae are a family of, for the most part, incon¬ 
spicuous plants, growing on rocks and stones in rivers and streams, 
and resembling mosses, seaweeds or lichens in their general 
appearance. They are submerged for the greater part of the year, 
and flowering takes place during the short time when the water is low 
and they are exposed to the air. An interesting feature of the 
group is the so-called “thallus,” which either creeps and branches 
close over the surface of the rocks or sends up erect branches 
which may again give rise to leafy shoots; in some cases the 
branches are produced endogenously, and their extremities may or 
may not be provided with a root cap, or they may arise exogenously, 
or again, as Mr. Willis has shown, both modes of origin may occur 
^Iem. de l’Acad. R. des Sci. et des lettres de Danemark, 6 me 
vSerie, Sect, des Sciences. T. xi., No. t, p. 37, 1901. 
