444. SECTIONAL TRANSACTIONS.—K. 
growing point of small embryonic cells is superficial. The tip of the strand, 
in growing longitudinally, presses radially inwards till it reaches the host 
cambium. ‘There its radial growth pari passu with the cambium establishes 
a sinker, which is therefore not comparable with a lateral root. 
The corresponding strands of Arceuthobium pusillum begin as filaments 
and grow in thickness by longitudinal division of the cells; the xylem is 
endarch. In Loranthus the parasite spreads as an amorphous mass of 
tissue. A Viscum from Mauritius shows a very irregular system. None 
of these justify homologising with ordinary categories of plant members. 
Having classified them as organs sui generis, progress is possible in two 
related directions. ‘These endophytic systems of the Loranthacez offer 
an opportunity for the study of tissue correlations—the behaviour of 
equipotent cells in different micro-environments. Secondly, a wide 
comparative study of them may yield clues to the evolutionary process in 
the group, which has evidently involved in a very special way changes in 
the behaviour of the developing organism. 
Dr. F. W. JANE.—The seeds and seedlings of Utricularia vulgaris L. (12.10). 
Capsules of Utricularia vulgaris L. were collected in Norfolk in August 
1932. Germination of the seeds did not start until May 1933: those from 
one capsule germinated over a period of eleven to twelve months. 
On germination, some six primary leaves emerge, to be followed rapidly 
by about as many more; while it is not possible always to separate these 
two apparent whorls, they are usually distinct. 
Associated with the primary leaves there is usually a primary bladder, 
a shoot and a small ‘adventitious shoot.’ The ‘adventitious shoot’ does 
not develop farther. 
The primary leaves are nearly always subulate and unbranched. The 
cauline leaves of the seedling generally consist of two lateral leafy segments, 
more or less branched, and a median bladder. The vascular strand to the 
leaf divides, shortly after leaving that of the axis, into three, one branch going 
to the bladder, the other two to the leafy segments of the leaf. ‘There is, as 
a rule, a single leaf at each node, but sometimes there are two. ‘The cauline 
leaves are subject to considerable variations, but these are nearly always due 
to reduction of parts of the trifurcate leaf of the seedling, which is above 
described, or to the replacement of the median bladder by a leafy segment. 
Most of the seedlings perennated as minute turions, which formed in 
November. Some seedlings were grown satisfactorily on moist soil and 
formed winter buds in autumn, but the opening of such turions in the 
following spring was erratic, this being due, it is suggested, to the unusual 
environment. 
Prof. J. SMALL.—Quantitative evolution (12.30). 
Quantitative evolution. Yule’s mathematical theory of evolution is 
confirmed in detail but modified by the old-age death of species. The 
apparent ages of groups, plotted against time in years, follow an exponential 
curve with the formula Dp.k + nd = T.2". For Composite, grasses, 
and angiosperms in general, k = 0:6, d = 0:9, T = 1:09375 m.y. From 
the properties of this BAT curve the following items are deduced : Species 
of angiosperms double in number each two million years and die when they 
have existed for 12 m.y., of senescent sterility, with chance playing no 
essential part in their decease. Ordinary genera become senescent after 
six doubling periods and die at 26 m.y., but primordial genera have a longer 
