448 SECTIONAL TRANSACTIONS.—K. 
the centre of the cotyledon, and the same thing is found in a few true Monocotyledonous 
species. These frequently have incipient poles in the cotyledonary plane also. 
Where the plane of the rodt poles does not (Diagonal type of Thomas) coincide 
with that passing through the centre of the cotyledons, the primary radial protoxylem 
elements, normally developed in the cotyledonary plane, though sporadically present, 
would seem to be disappearing phylogenetically as well as ontogenetically. The 
phenomena to be observed in the following species may perhaps be regarded as stages 
in this process: Calycanthus, Thomas 1914; Alnus cordifolia, Davey 1915; Sapo- 
tacee, Wright 1902, Thomas 1922; Acer pseudoplatanus, Holden and Bexon 1923. 
4. The study of the hypocotyledonary region gies the truest picture of the 
fundamental anatomical structure of the seedling. The cotyledon strands may vary 
in number and constitution, in species which show identical hypocotyl structure, so 
that the number of cotyledon strands in no sense ‘ controls’ the number of groups 
in the hypocotyl. Moreover, hypocotyl structure may be unaffected even by variation 
in the number of cotyledons developed. This is shown by comparison of Monocoty- 
ledons, Dicotyledons, Polycotyledonous Conifers, and in particular by Pseudo- 
monocotyledons (Thomas 1914) and Pseudo-dicotyledons (Coulter and Land 1914). 
5. That the characteristic alternate grouping of cotyledonary and hypocotyl 
strands is not a ‘ transition ’ phenomenon—a ‘ carrying up’ of root strands is shown 
by the presence of this grouping in the plumule (Thomas 1914, Davey 1915, Bugnon 
1920, Holden and Bexon 1923) and by its production in the cotyledonary plane, even 
where root poles are developed only in the diagonal planes. 
Conclusions: 1. That there is a remarkable uniformity in the main features of 
seedling anatomy, particularly as displayed in the hypocotyledonary region. 
2. That this uniformity has been obscured by developmental changes, notably 
by ‘ resorption ’ (which converts a single ‘ alternate’ group into two collateral strands) 
and by errors in descriptions and conclusions, largely due to these changes. 
3. That Van Tieghem’s types should be abandoned. They no longer serve a 
useful purpose since they depend upon criteria (rotations and number of strands) 
which the work of the present century, when duly compared and considered, proves 
to be false criteria. The terms cruciform and diagonal may temporarily be allowed to 
distinguish the only important difference of position known. Cruciform connotes 
the almost universal production in the root of poles in the plane of the centre of the 
cotyledon and Diagonal the rare condition of the production of the root poles at 45° 
to this plane. 
4. That the hypocotyl is the region of greatest constancy and that its alternate 
or radial structure is probably of phylogenetic import, and that the number of strands 
in the cotyledon and even the number and size of the cotyledons themselves bear 
little relation to the number of primary groups in the axis. 
5. That the phylogenetic theories of Sargant, Thomas and Chauveaud stand for 
further consideration, but that the relation between Monocotyledon and Dicotyledon 
rests on the ‘symmetry ’ of the hypocotyl and not on the suggested significance of 
the two central strands of the single cotyledon of Monocotyledons. 
6. That Seedling Anatomy provides a new field for work in Embryology, Compara- 
tive Anatomy, Organography, and particularly for consideration of the relation between 
structure and function, Phylogeny and Ontogeny and Heredity and Environment. 
13, Dr. A. B. Renpiz, F.R.S.—EKarly Botanical Exploration im 
British North America. 
14. Mr. R. D. Goopv.—The Past and Present Distribution of the 
Magnoliee. 
The paper is an attempt to review the pre-Darwinian hypothesis of climatic 
migrations, put forward by Prof. E. Forbes in 1845, in the light of our subse- 
quent increase of knowledge. For this purpose a homogeneous and well-defined 
group of plants—the Magnoliew—has been selected and its history and distribu- 
tion carefully analysed and considered. 
A short introduction, outlining Forbes’ theory, is followed by some general 
remarks upon the systematics and biology of the group. Their general recent 
distribution is then described and is followed by detailed accounts of the indi- 
vidual genera. After this the influences of climatic factors are discussed. Next, 
the fossil record is considered, and this is followed by a survey of our know- 
