Scott and Hill.—Struchire of Isoetes Hystrix. 415 
through the whole length or thickness of the stem has proved 
of great advantage 1 . 
The Guernsey specimens of Isoetes Hystidx are small, the 
extreme length of the leaves not exceeding two inches, while 
the full diameter of the bulbous stem reaches about half an 
inch. The upper part of the short stem is covered by the 
swollen, sporangiferous bases of the living leaves, while 
the lower portion is enclosed in an armour of the persistent, 
spinose bases, almost black in colour, of the leaves of previous 
years. As is well known, the cortex is not, as a rule, thrown 
off in the terrestrial species of Isoetes , or only very slowly, 
so that the whole stem, or all except the oldest part at the 
base, remains protected by the spines. 
All the specimens we examined had three furrows, separat¬ 
ing three well-marked lobes. This is almost constant in the 
species, though four-lobed specimens have been described. 
Admirable illustrations of the habit of Isoetes Hystrix will 
be found in the monograph by Motelay and Vendryes, 
Plates XV and XVI 2 . The appearance of the three-furrowed 
stem, as seen from below, after removing the roots and spiny 
leaf-bases, is shown in our Plate XXIV, Fig. 29. The 
Guernsey plant appears to belong to the variety snbinermis, 
of Durieu, as shown by the shortness of the spines (see 
Fig. 28), though the stems have not usually undergone the 
early desquamation, stated by Motelay and Vendryes (p.490) 
to characterize this variety. 
As the plant grows, in nature, the whole of the bulbous 
portion, including the bases of all the living leaves, is com¬ 
pletely buried in the soil, so that only the tuft of narrow, 
green leaf-blades is exposed to view. Thus no sign of the 
presence of fructification is visible externally, and we have 
the rare case of a plant with subterranean organs of repro- 
1 I desire to place on record that the great majority of the preparations, and the 
whole of the drawings, were the work of my colleague, Mr. T. G. Hill. On the 
other hand, I assume all responsibility for the theoretical views expressed at the 
conclusion of the paper.—D. H. S. 
2 For works cited, see the list of literature at the end of the paper. 
