Mar., 1904 .] Extra-Floral Nectaries and Glands. 
105 
insects may serve as food to the captor. Some of the Ohio 
thistles also have glandular involucral bracts. 
Various plants have gland tipped teeth or serrations, as species 
of Salix, Populus, Prunus, and other genera. In some plants 
the stipules have prominent nectar glands or are reduced to 
nectaries. Other gland- like stipules however do not appear to 
secrete nectar. Among the genera which contain species with 
glandular or gland-like stipules, the following may be mentioned : 
Reseda, Linum, Euphorbia, Isnardia, and Circaea. 
The more important glands of special interest are those which 
secrete nectar or those which have attained considerable morpho- 
logical development. Although it is not easy to make a classifi- 
cation of extra-floral glands because of the indefiniteuess of these 
structures, an arbitrary arrangement will be given below to 
indicate in a general way their origin and position. Some of the 
special types I have not yet found on Ohio plants as for example 
the pit-like nectar glands on the lower surface of the midribs of 
the leaves of Gossypium herbaceum and other plants. The fol- 
lowing types are known to occur in Ohio : 
1. Glands which ajrpear on the margin at the base of the 
blade or on the top or the sides of the petiole and evidently 
representing highly specialized glandular teeth or serrations ; as 
in Populus and Amygdalus. 
2. Highly developed glands under the lobes or teeth of the 
blade ; as in Ailanthus. 
3. Special patches of tooth-like glands appearing like modified 
hairs or eruptions either at the upper or lower end of the petiole 
or at both ; as in Asclepiodora and Asclepias. 
4. Patches of pit-like nectaries on the upper side at the lower 
end of the petiole : as in Tecoma. 
5. Single or few nectaries on the petiole not apparently 
originating from hairs, serrations, leaflets, or stipules ; as in 
Cassia and Ricinus. 
6. A series of nectaries on the rachis between the successive 
pairs of leaflets or divisions ; as in Acuan. 
7. Glands on the under side of the leaf in the axils of the 
veins or on the ranchis at the base of the divisions ; as in Catalpa 
and Pteridium. 
8. Glands on the rachis apparenth' representing modified 
leaflets or stipels ; as in Sambucus. 
9. Glands on the stipules or rej^resenting highly modified 
stipules ; as in \ 4 cia and Circaea. 
10. Glands on the calyx or peduncle not showing any evident 
relation to pollination ; as in Tecoma, Paeonia, and Ricinus. 
1 1 . Glands on submerged water plants ; as in certain species 
of Potamogeton which have two glands at the base of the leaf 
blade. 
