SECTIONAL TRANSACTIONS.—K. 557 
successive phellogens. The ‘ growth zone’ resembles an inverted cup 
with a hole in the bottom—i.e. beneath the apex of the tuber. Apex and 
base are further developed from the surrounding meristem and respectively 
produce a sympodium with reduced internodes and fibrous roots. 
Adventitious buds may develop when a fissure penetrates beneath the 
‘ growth zone ’ and causes its cells to collapse in that area. The conditions 
thus brought about are comparable with those obtaining at the tuber apex. 
Miss L. M. Wicxs.—The significance of the inverted bundle system (11.20). 
In Amaryllidaceous leaves the development and course of the vascular 
system was studied, especially in concentric leaves on account of the presence 
of two systems of vascular bundles : (i) a system of large normally orientated 
bundles ; (ii) an adaxial system of small inverted bundles. Throughout 
the leaf-limb the two systems are connected by transverse commissures. 
In the leaf-base the relationship of the inverted bundle system to the 
normally orientated one and to the stem system varies, and the following 
three types were found : 
(1) The Ianthe type—Certain normally orientated bundles in the bi- 
facial leaf-base curve round and enter the concentric leaf-limb as inverted 
bundles. 
(2) The Agave type—The inverted bundles are formed by special 
branches given off from the normally orientated bundles in the leaf-base. 
(3) The Narcissus type-—The most marked variation occurs in Narcissus, 
where the inverted bundles pass down from the leaf-limb into the upper 
part of the leaf-base, where they end abruptly in groups of small tracheids. 
According to the Phyllode theory the concentric monocotyledonous 
leaves are morphologically petioles, the inverted bundles resulting from the 
flattening of a petiole with a circle of vascular bundles as seen in transverse 
section. It is difficult to see how such variations as shown in the three types 
here enumerated can be made to fit in with the phyllode theory. 
The inverted bundles can be considered as secondary structures developed 
during the evolution of the primitive monocotyledonous leaf, possibly to 
increase the amount of vascular tissue in order to supply the increased 
amount of assimilating tissue of the concentric leaf. 
Prof. G. Senn.—The influence of light on the permeability of the plant 
cell (12.0). 
AFTERNOON. 
Business MeerInG of the Section (2.0). 
Discussion on The teaching of botany in courses of biology (3.30). 
Prof. J. R. MatrHews.—Semi-popular lecture—The British flora and 
some of its problems (5.0). 
Wednesday, September 13. 
Visit to demonstration by the Timber Fireproofing Co., Ltd., Market 
Bosworth (10.0). 
