1920-21.] Size, a Neglected Factor in Stelar Morphology. 21 
vascular tracts may be rounded off, and each completely surrounded by its 
own endodermis (fig. 19). The stele is thus disintegrated into a number 
of meristeles, and the analogy 
with the ferns is significant. 
But all large Angiospermic 
roots do not behave in this 
way. A prominent exception 
is seen in Pandanus, the large 
prop-roots of which may he 
as much as 5 cm. in diameter, 
and yet show no stelar dis- 
integration. Thus size does 
not always prescribe it. These 
Fig. 18 . — Transverse sections of root of Areca. references by no means ex- 
i-iv, Successive sections from the same root: i is 15 mm. from L 0110 i. f n. 0 avomnloa wViinVi 
apex ; ii at 77 mm. ; iii at 115 mm. ; iv at 150 mm. v is a naUSt me examples WUlCn 
section from another, larger root. After Cormack. m i gh t be quoted £rom the 
higher vascular plants, in which distension, with or without a definite 
cambial zone, results in a distended mass of tissue. In such cases the 
texture is often sappy, and the 
vascular system broken up into 
numerous isolated strands. This 
is seen in Welwitschia, Gycas, 
Gunnera, and Nymplicea. It is 
worthy of remark that these 
plants, which resemble the Marat- 
tiacese in their general construc- 
tion of the stem though not in its 
details, are all either actually 
xerophytes, or they live under 
circumstances in which a rapid 
fluid-transit is not necessary. 
Nevertheless, that actual size Fig. 19, — Transverse section of a large strut-root 
is causally related to these abnor- °J rersclutfeUia splendida, showing high state 
J 01 stelar disintegration. 
malitieS in the roots of palms is st.— a completely cylindrical meristele. 
. 1 i n lr. = lateral roots. (x2). After Cormack. 
shown by the tact that when the 
root diminishes progressively the abnormality ceases. It was demon- 
strated by Cormack (Trans. Linn. Soc., vol. v, pt. 6, 1896) that there is 
a continuous transition to normal monostelic structure in the younger 
and thinner parts of roots that are fluted in their older and thicker 
region (fig. 18). He was led to conclude that this difference of structure 
