196 KANSAS UNIVERSITY SCIENCE BULLETIN. 



middle by a stalk-like arrangement. The stalks are usually 

 embedded in the epidermis. The hair is raised upon a pedestal 

 and the cuticle of the epidermis is continued on up around the 

 pedestal. This is similar to that found in Janusia. In 

 Calycanthacese unicellular trichomes are found having two 

 arms and a stalk. This stalk fits into the epidermis and is 

 surrounded by a rosette-like arrangement of the epidermal 

 cells. This rosette arrangement is like that found surrounding 

 the stalk of Janusia. The CruciferEe furnish examples where 

 the stalk of the trichome extends down below the epidermal 

 cell layer. In the Pittosporeae the hairs resemble those of 

 Janusia, except that the stalk is multicellular, while that of 

 Janusia is but part of the whole hair. Hairs with papillae are 

 not of an uncommon occurrence. This is a characteristic of 

 the hairs of Janusia. 



In figure 29 is shown a cross section of the leaf and hair in 

 position. Its stalk tapers to a round point (fig. 29, A). The 

 point is cutinized, but the upper portion of the stalk, including 

 the rest of the entire hair, is cellulose. In cross and longi- 

 tudinal sections the hair seems to be hollow. 



It is held in place by the continuation of the outer walls of 

 the epidermal cells, which is cutinized as far up as to the at- 

 tachment of the hair (fig. 29, B). This membrane holding the 

 hair in place fastens to the cell surrounding the pore at about 

 the middle of their upper surface. These cells surrounding 

 the pore have walls with a thicker cutinized substance than 

 the adjacent cell walls. 



As is seen, the palisade cells extend up directly against the 

 pore. It is evident that the trichome has developed from one 

 cell and that it has become broken loose from those cells sur- 

 rounding it, thus leaving it loose to move up and down. In 

 this way it may form a plug in the pore at times and leave it 

 open at other times. Whether the protoplasm has been dis- 

 organized has not been determined. At different times the 

 hair has been found collapsed. 



The epidermal cells have a depth of about .018 mm., and 

 have a thick outer cutinized wall. The palisade cells are very 

 compact and leave but little intercellular space. In length they 

 are about the average, but in width they are very narrow, 

 having a width of about .01.5 mm. (figs. 24 and 29). The 

 chloroplasts are very small and very numerous. These pal- 



