354 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
The rubrinervis is in many respects a counterpart to the gigas, but 
its stature is more slender. The spikes and flowers are those of the 
lamarckiana, but the bracts are narrower. Red veins and red streaks 
on the fruits afford a striking differentiating mark, though they are 
not absolutely lacking in the parent-species. A red hue may be seen 
on the calyx, and even the yellow color of the petals is somewhat 
deepened in the same way. Young plants are often marked by the 
pale red tinge of the mid-veins, but in adult rosettes, or from lack of 
sunshine, this hue is often very faint. 
The leaves are narrow, and a curious feature of this species is the 
great brittleness of the leaves and stems, especially on annual indi- 
viduals, for example, on those that make their stem and flowers in 
the first year. High turgidity and weak development of the mechani- 
cal and supporting tissues are the anatomical cause of this deficiency, 
the bast-fibres showing thinner walls than those of the parent-type 
under the microscope. Young stems of rubrinervis may be broken 
off by a sharp stroke, and show a smooth rupture across all the tissues, 
while those of lamarckiana are very tough and strong. 
Both the giant and the red-veined species are easily recognized in 
the rosette-stage. The very young seedlings of the latter are not 
clearly differentiated from the lamarckiana, and often a dozen leaves 
are required before the difference may be seen. Under ordinary 
circumstances the young plants must reach an age of about two 
months before it is possible to discern their characters, or at least 
before these characters have become reliable enough to enable us to 
judge of each individual without doubt. But the divergencies rapidly 
become greater. The leaves of O. gigas are broader, of a deeper 
green, the blade more sharply set off against the stalk, the whole 
rosettes becoming stout and crowded with leaves. Those of O. rubri- 
nervis on the contrary are thin, of a paler green and with a silvery white 
surface; the blades are elliptic, often being only 2 cm. or less in width. 
They are acute at the apex and gradually narrowed into the petiole. 
It is quite evident that such pale narrow leaves must produce 
smaller quantities of organic food than the darker green and broad 
organs of the gigas. Perhaps this fact is accountable partly, at least, 
for the more robust growth of the giant in the second year. Perhaps 
also some relation exists between this difference in chemical activity 
and the tendency to become annual or biennial. The gigas, as a rule, 
produces far more, and the rubrinervis far less biennial plants, than 
the lamarckiana. Annual culture for the one is as unreliable as 
