SECTIONAL TRANSACTIONS.—K. 443 
SECTION K.—BOTANY. 
Thursday, September 5. 
Prof. E. J. Satissury, F.R.S.—The East Anglian flora (10.0). 
The East Anglian flora is a peculiarly rich one. The Continental Com- 
ponent is the most fully represented, with 78 per cent. of the total species 
of this category present in Britain. All the steppe species of the British 
flora are found in East Anglia, and over go per cent. of those more definitely 
restricted to continental climatic conditions on the European mainland. 
It is therefore apparently paradoxical to find that the other Component 
best represented is the ‘ Oceanic Component,’ with 59 per cent. of the 
British species of this category. Forty-eight per cent. of the ‘ Southern 
Component,’ 13 per cent. of the ‘ Northern Component,’ and about a 
quarter of the British endemics, are also present. 
The apparent heterogeneity of the flora of East Anglia can be related to 
a striking diversity in the edaphic-climatic complex and by comparative 
study it can be shown that the migration factor is unlikely to have played 
any significant part in determining the richness of the flora of this region 
as compared with others. ‘The flora of East Anglia is a striking testimony 
to the importance of ecological conditions in determining the distribution 
of species. Under favourable environmental conditions, historical factors 
would appear to affect abundance far more than frequency. 
Miss E. R. SauNDERS.— Some floristic problems and their solution (11.0). 
It is generally acknowledged that the regular alternation of successive 
floral whorls is the outcome of an inherent rhythm. Such rhythm is 
undoubtedly common to all flowering plants, yet in many species it appears 
to break down. ‘The explanation hitherto offered of such breakdowns is 
either that an intervening whorl, originally present, has disappeared, or that 
one of two successive superposed whorls is not of the order of a true whorl, 
but is an appendage of the other. Neither explanation is satisfactory. 
The former is unsupported by evidence, the latter is not even a plausible 
fiction. A study of the vascular ground-plan shows that both assumptions 
are gratuitous. Except in one particular set of conditions an alternating 
rhythm is maintained throughout the flower, but this alternation is primarily 
between successive whorls of vascular units and may or may not hold 
between successive whorls of floral members. If the midrib bundles are 
initiated independently for each whorl the whorls of members alternate as 
well as the whorls of midribs. But if the midribs of two superposed whorls 
are derived from a common source, i.e. are organised from the same vascular 
unit, then two such whorls behave as a single whorl in the scheme of alterna- 
tion. It follows that the solution of problems of whorl arrangement is to 
be found in the vascular scheme. 
Prof. D. THopay.—The apical growth of the strands of mistletoe in the 
cortex of the host (11.40). 
Re-examination of the cortical strands of Viscum album, by some regarded 
as modified roots, suggests that a deeper study of their development and 
behaviour is necessary before homologies can usefully be discussed. ‘The 
apex is fringed by hyphal cells with thick gelatinous walls, but the actual 
