ON 'THE LEAVES OF THE BRACKEN, 659 
Puate 22. 
Fig. 7. Pinus Coulteri, showing 3-sided leaf, thick hypoderm projecting 
inwards in wedge-like masses; mesophyll-cells plicated ; resin-canals 
median and internal, without stereome-sheath; endoderm of about 
70 cells; meristele somewhat triangular in section; branches of the 
fibro-yascular bundle separate at the base by a mass of stereome-cells 
projecting from a horizontal band of similar cells, in contact with the 
lower surface of the phloem. 
Fig. 8. Pinus Pinea, cotyledon 3-sided; epidermis and hypodermis feebly 
developed; cortex-cells not infolded; resin-canals subepidermal, 
with no stereome-sheath ; meristele subtriangular ; fibro-vascular 
bundle simple ; endoderm-layer of about 35 cells, irregular. Compare 
the appearances with the adult structure described in the text. 
Puiats 23. 
Fig. 9. Pinus Lambertiana, primordial leaf with two very large subepidermal 
resin-canals and a single fibro-vascular bundle; epiderm, endoderm, 
and hypoderm imperfectly differentiated. Compare this with the 
fully-developed structure of the adult leaves (see text). 
Fig. 10. Pins Bungcana, leaf-section somewhat. triangular ; resin-canals sub- 
epidermal, surrounded by stereome-cells; cortical cells radiating 
from the central cylinder ; endoderm-cells about 24; fibro-vascular 
bundle simple. 
Fig. 11. Pinus maritima, var. Hamiltoni, section semi-cylindric or boat- 
shaped ; epiderm broken by stomata on all sides; hypoderm double ; 
cortical layer showing palisade-cells ; endoderm-cells about 50; 
meristele oblong in section, slightly depressed on the upper surface ; 
fibro-vascular bundle branched, with little or no stereome between 
the branches. 
The Structure of the Leaves of the Bracken (Pteris agutlina, 
Linn.) in relation to Environment. By L. A, Boopre, 
F.L.S. (With 5 text-figures.) 
[Read 5th November, 1903. } 
Ir is a familiar fact that the bracken, though little variable in 
its choice of soil, grows in very diverse habitats, e. g., on dry 
heaths and also in damp and deeply shaded copses. It has been 
observed that certain external characters are typical of the 
specimens which grow in exposed and in sheltered places respec- 
tively. Thus Druery (Gardeners’ Chronicle, no. 822, 1902, 
p- 228) mentions that deep shade and shelter from wind bring 
about a more foliose and spreading habit, while exposure tends 
