TRICHOMES OF PAP AVER HYBRIDS AND PURE SPECIES. 13 



(figf. 2, ^). Somewhat away from the tip there are 2 cells in cross-section, 

 still further there are 3 cells, and the number of cells of the cross-section 

 increases as one goes towards its base. At the base the trichome expands 

 suddenly, so that in longitudinal section it is conical. All of the cells of 

 the trichome are elongated in a direction parallel to its longer axis. The 

 increase in length takes place at the tip of the trichome, where new cells are 

 cut off by somewhat oblique walls. Growth in diameter appears to occur 

 by longitudinal divisions of the inner cells, but the exact sequence of these 

 divisions was not studied. The trichomes of the three species are similar 

 in form and size, but they are unlike in quality of roughness. In Papavcr 

 orientate and Papaver pilosum the distal ends of the superficial cells project 

 beyond the general surface of the trichome and turn out at a rather acute 

 angle (fig". 2, c, d, and e). In Papaver somniferum, however, these cells did 

 not extend beyond the general surface, with the effect that the trichomes 

 of this species are smooth (fig. 2, a). 



The leaves, stem, and flower-stalk of Papaver orientate and of Papaver 

 pilosiim are well clothed with trichomes; but Papaver somniferum is prac- 

 tically glabrous, as only a few trichomes were observed on the flower-stalk, 

 and none on stem or leaf. 



PAPAVER SOMNIFERUM X PAPAVER ORIENTALE. 



The leaves and the stem of the hybrid are well covered with trichomes, 

 which in size and in form resemble those of Papaver orientate, but in certain 

 regards they are unlike the trichomes of that species. They, also, are dif- 

 ferent from the trichomes of Papaver somniferum, and in each instance the 

 variance lies in the character of the peripheral cells. The distal ends of 

 the peripheral cells, which in the seed parent are suppressed, but which 

 project with much regularity in the pollen parent, in the hybrid are ex- 

 tremely variable in their behavior. In some instances they do not project 

 at all, in others the projection is well marked, perhaps accentuated, and 

 frequently a middle condition was noted (fig. 2, /). In this particular, 

 therefore, the hybrid is fairly intermediate and exhibits the influence of 

 both parents. 



PAPAVER SOMNIFERUM X PAPAVER PILOSUM. 



The hybrid Papaver somniferum X Papaver pilosum is especially well 

 covered with trichomes which closely resemble those of the other Papaver 

 hybrid studied. That is, in one character, namely, that of the surface of 

 the trichomes, they are intermediate between the pure parents. The pro- 

 jections of the superficial cells are, if anything, even more irregular than 

 in the other hybrid (fig. 2, h and z). In some instances the projections 

 are suppressed entirely, in others they are exaggerated and the trichome 

 has the appearance of bearing branches, but an intermediate condition also 

 occurs. This variation is suggested, but nowise adequately shown, in the 

 accompanying sketches. 



