Physiological Anatomy of the Vascular Plants. 267 
APPENDIX. 
Notes on Microchemical Examination of Yorkshire Peat Plants.* 
Calluna vulgaris Hull. 
Clearly marked secondary endodermis, without gaps, in young 
green stems about one inch in length . Endodermis cells relatively 
large and conspicuous. Nearer the growing point, a primary 
endodermis with casparian strip is indicated. Older stems 
showed, external to the phloem, three or four rows of suberised 
cork cells within the endodermis ; the cortex withering and 
easily crumbling away outside the cork. In the root, within 
the withered cortex, several layers of cork. 
Erica Tetralix L. 
In young stem a secondary endodermis present fairly early, in 
the older stem several rows of suberised cork cells form within 
this. 
Andromeda Poli folia L. 
The old stem showed a deep seated layer of cork, 3 — 4 cells deep, 
arising probably within a secondary endodermis. The leaf 
showed a remarkable quantity of fat deposits. 
V accinium Myrtillus L. 
A complete secondary endodermis within the young green stem, 
and just within this is a ring of sclerenchyma. In the older stem 
cork arises within this ring of sclerenchyma. 
V accinium Oxy coccus L. 
A well marked cork layer (3 — 4 rows) present in youngest stems 
available, it is deep seated and appears to lie within a tangentially 
flattened secondary endodermis, which is crushed between the 
cork and a ring of sclerenchyma just outside it in the cortex. 
Older stems showed thicker cork layers with the cortex disinte- 
grating. 
Empetrum nigrum L . 
In the young stem, just behind the growing point, much fat was 
present in the phloem, but no suberin deposited in the walls 
outside the phloem. A little lower down, occasional cells of the 
endodermis showed a suberin lamella, a little lower again (within 
an inch of the tip) a complete secondary endodermis was present. 
This anatomical modification appears associated with a change 
in the colour of the stem from green to red. In older stems cork 
appears within the endodermis, and the cortex and endodermis 
begin to disintegrate and disappear. 
Galium saxatile L. 
A well marked cuticle and complete secondary endodermis even 
in the flowering axis. 
Potentilla Tormentilla Neck. 
Conspicuously large endodermis cells, with suberin lamella and 
casparian strip, present in the flowering axis. 
Rubus Chamcemorus L. 
No indication of secondary endodermis in the leaf stalk ; re- 
latively thin cuticle. 
Ulex europaeus L. 
(Hardly a typical peat plant). In the soft green stem no in- 
dication of a secondary endodermis, although fat appears to be 
present in the phloem. In the older brown stem several rows 
of cork are present just external to the phloem, and in still older 
stems the outer cortex with its angular outline has rubbed away. 
* Sections of many of these plants will be on view at the Y.N.U. 
exhibit during the British Association Meeting at Hull. 
1922 Aug.-Sept. 
