420 MINNESOTA BOTANICAL STUDIES. 



larger on the upper surface than on the lower. These cells 

 have a very sinuous outline when seen in surface view. Sto- 

 mata are confined to the lower leaf surface. A loose palisade 

 layer lies next to the upper epidermis. The spongy paren- 

 chyma below this has large air cavities. A few short, clavate, 

 unicellular trichomes sometimes occur on the under surface of 

 the leaf. 



Anatomy of the foliage leaves. The leaves have sheath- 

 ing bases and channeled petioles. In the center of the petiole 

 there is an air cavity. Five or more vascular bundles form a 

 circle outside this cavity. (See Fig. 13.) Each bundle con- 

 sists of a large mass of xylem, a very small amount of phloem 

 and, external to this, a small mass of stereom with lignified cell 

 walls. The fundamental tissue is loose parenchyma. No 

 special hypoderma is developed. The epidermis is thin-walled. 

 The leaf laminae are thin and composed of very loose tissue. 

 The epidermal cells are large and have sinuous outlines. An 

 interesting peculiarity is to be noted in the palisade. The cells 

 of this tissue are frequently branched at the upper end. (See 

 Fig. 15.) This peculiarity was noted, according to Solereder,* 

 by Haberlandt in certain species of allied genera, but that 

 investigator failed to find branched palisade cells in any of the 

 species of Delphinium which he studied. The stomata of the 

 foliage leaves are confined to the lower surface of the leaf. A 

 row of short, simple, pointed trichomes is placed along the 

 margin of the leaf and a very few similar trichomes are scat- 

 tered on the upper surface. 



EXPLANATION OF FIGURES, PLATE XXVIII. 



Figures i, 2, 3. Seedlings of Delphinium occidentale in various 

 stages of development (natural size). In Figures i and 2 the united 

 petioles of the cotyledons have the appearance of a hypocotyl. In 

 Figure 2 the first leaf appears as a small projection at the base of the 

 petioles of the cotyledons. 



Figure 4. Seed, x 18. 



Figure 5. Longitudinal section of seed showing the minute embryo. 

 The dotted ellipse indicates the line of division between the inner, oily 

 portion of the endosperm and the outer part containing aleuron grains. 

 X 18. 



* Solereder. Sjst. Anat. der Dicotyledonen, 18, 



