34 EDITH SCHWARTZ CLEMENTS 



lower 20/n; cuticle, upper 2 p., lower thin; chlorenchym (305/4) 2 

 lacunose rows prolate palisade cells 75 p. ; lacunose star-shaped 

 sponge cells. (Plate II, fig. n.) 



Polemonium speciosum: leaf 325/4; epidermis 20/4; cuticle thin. 



Erigeron superbus: leaf 300 p.; second row of palisade cells in- 

 definite, transforming into sponge cells. 



Open spruce: light o.i ; available water 12-16%; humidity 40- 

 70% ; temperature 48-72. 



GYROSTACHYS STRICTA : spongophyll 350 p. ; epidermis, upper 50 p., 

 lower 30/1; cuticle 5/11; chlorenchym (270/1) uniform subglobose 

 cells. (Plate III, fig. I.) 



Zygadenus elegans: leaf 300 p. ; epidermis 50 p.. 



CASTILLEIA SULPHUREA: diplophyll 160/4; epidermis 15/4; cuticle 

 thin; chlorenchym (130/4) i loose row subglobose to prolate cells 

 next to either epidermis ; central loose oblate and prolate cells. 

 (Plate III, fig. 2.) 



Castilleia sp. : leaf 200 p. ; epidermis 20 /4. 



CASTILLEIA CONFUSA : diphotophyll 190 p. ; epidermis 20 p. ; cuticle 

 thin; chlorenchym (150/4) I close row prolate palisade cells 60/4; 

 close subglobose sponge cells. 



The spongophyll is the characteristic form of monocotyledonous 

 types. The very large-celled epidermis of Limnorchis, Streptopus 

 and Vagnera is probably an adaptation for the furthering of trans- 

 piration. It is extremely well developed in these three wet-soil 

 shade-plants, and is also large for other shade-plants living in a 

 rather high percentage of soil-water. Calypso boreale, although 

 placed with Adoxa moschatellina as a shade-plant, has a thick cuticle, 

 indications of two rows of palisade cells, and a more compact struc- 

 ture. These facts indicate that the ancestors of Calypso were sun- 

 plants, and that hereditary structure has not as yet yielded to any 

 extent to the influence of shade conditions. 



The type of leaf most common among dicotyledonous shade- 

 plants is that of Parietaria pennsilvanica and Geranium richard- 

 sonii. Adaptations for an increase of transpiration are the thin 

 cuticle, and the loose sponge tissue, as well as the wavy epidermis 

 and surfaces. The effects of the diffuse light are to be found in 

 the thinness of the leaf, the reduction in chloroplasts and palisade 

 cells, and the oblate shape of the sponge cells. Erodium cicutarium, 

 which is a ruderal plant growing in moist sunny situations, is similar 



