THE AMERICAN BOTANIST. 51 



considerable morplK^logical development. Although it is 

 not easy to make a classification of extra-floral glands be- 

 cause of the indefiniteness 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 following 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 evi- 

 dently 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 As- 

 clepias. 



4. Patches of pit-like nectaries on the upper side at 

 the lower end of the petiole ; as in 7'econia. 



5. Single or few nectaries on the petiole not apparent- 

 ly originating from hairs, serration, leaflets or stipules ; 

 as is Cassia and Ricinus. 



6. A series of nectaries on the rachis between the suc- 

 cessive pairs of leaflets or divisions ; as in Acuan. 



7. Glands on the under side ot the leaf in the axils of 

 the veins or on the rachis at the base of the divisions; as 

 in Catalpa and Pteridium. 



8. Glands on the rachis apparently representing mod- 

 ified leaflets or stipels ; as in Sambucus. 



9. Glands on the stipules or rej^resenting highly mod- 

 ified stipules; as in Vicia and Circasa. 



10. Glands on the cal^^x or peduncle not showing any 

 evident relation to pollination; as in Tecoma, Pasonia 

 and Ricinus. 



11. Gland on submerged water plants; as in certain 

 species of Potamogeton which have two glands at the 

 base of the leaf blade. 



