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 indefiniteness of these 

 structures, an arbitrary arrangement will be given below to 

 indicate in a general wa}- 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 appear 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 apparently representing modified 

 leaflets or stipels ; as in Sambucus. 



9. Glands on the stipules or representing highly modified 

 stipules ; as in Vicia and Circaea. 



10. Glands on the calyx or peduncle not showing any evident 

 relation to pollination ; as in Tecoma, Paeonia, and Ricinus. 



11. Cjlands on submerged water plants ; as in certain species 

 of Potamogeton which have two glands at the base of the leaf 

 blade. 



