254 
The A natomy of the Mummy Pea. 
we obtain, according to the concrescence theory, a ring-fasciation. 
Now assuming that the vascular bundles which lie near the points 
of contact of the component stems (those on the common radii in 
the figure) are obliterated, we. are left with an external and an 
internal system of vascular bundles: those of the latter are fewer 
in number and have an inverse orientation. (In the diagram the 
the two systems are joined up respectively by dotted lines). 
Fig. 4. Geometrical construction for ring-fasciation on the theory of 
concrescence. 
Thus while denying that a ring-fasciation is actually produced 
by concrescence, we may obtain by this analytical method an 
insight into the origin of its anomalous structure. 
It also appears that in certain cases a ring-fasciation may be 
produced by the invagination of the external tissues. This is the 
interpretation put by Richter 1 on certain abnormalities in Helianthus 
annuus. If we consider these two methods of the formation of 
ring-fasciations, we are forcibly reminded of the two rival theories 
that have been advanced to account for the medullation of the 
stele in Pteridophyta, Pteridospermse, etc. The method of direct 
tubulisation described for the Mummy Pea may be compared with 
the theory of the intrastelar origin of the pith : while the method 
1 P. Richter “ Ueber Missbildungen der Bliithenkopfe der 
Sonnenbtume.” Ber. d. d. Bot. Ges. VIII., p. 231, 1890. 
