182 
velop the power of starch formation within the chlorophyll grains. 
As starch is stored abundantly in Zalinum teretifolium, it may be 
that the potassium chloride plays this réle, but this has not been 
certainly determined. It is interesting, however, to note that the 
phosphate of magnesium is present in the perennating stem, hav- 
ing been taken up by the roots. Whether its presence in the 
plant determines the plant’s distribution is still a physiological 
enigma. 
The plant has been recorded from other formations. Gray's’ 
manual saysserpentine rocks. Upham* records it as occurring on 
ledges of rock (trap, syenite, granite and quartzite). It was found 
by Hill in the silicious sands at Miller’s, Lake County, Indiana. 
In Illinois, it is found on sandy prairies and barrens, At Taylor’s 
Falls, three other plants are associated with it on trap rocks, viz.: 
Campanula rotundifolia, Selaginella rupestris and Cladonia rangi- 
ferina. A mention of the habit of the plant in other places than 
southeastern Pennsylvania shows that Zalinum teretifolium chooses 
many different soil formations, and the name of one locality Arena, 
Wisconsin, is suggestive. 
Several species of the genus 7a/inum were found by me in 
Mexico this last summer growing on the bare faces of rocks. On — 
the Cerrode Guadalupe, a rocky hill on the south front of which 
is situated the Holy Shriné“ of Our Lady of Guadalupe” 
(Nuestra Senora Guadalupe) were found two species on the face 
of the weather worn rocks, namely 7: pafens and 7. aurantiacum. 
These plants grew in an extremely dry situation, and exposed to 
the full blaze of the sun. The flat succulent leaves of 7: padens 
were rolled up at their edges, so that the plant had a peculiarly 
curled appeared. This was no doubt an adaptation on the plant’s 
part to meet the direct rays of the sun. The root of this plant is 
large, fleshy and succulent, and penetrates to a considerable depth 
(8-10 in.) into the crevices of the rocks. 
consolidated more than 7. patens, and hasa strong swollen tap- 
root, somewhat tuber-like in appearance. The leaves are linear, 
thick and grooved by two longitudinal grooves, as if the mar- 
gin had been inflexed. Two other Mexican species 7. Green- : 
mani and 1. napiforme were discovered on exposed volcanic — 
* 1891. Upham, Botan, Gaz. 16: 112. : Te 
; 
7. aurantiacum-—is 
a a 
