TRICHOMES OF SOLANUM HYBRIDS AND PURE SPECIES. 15 



The giant awn-shaped trichomes are different from the awn-shaped ones 

 mainly in the quality of size; they measure from 792 /* to 1.4 mm. No tri- 

 chomes were observed of the awn- shaped type which measured longer 

 than the longest awn-shaped trichomes, 352 /*, or shorter than the shortest 

 giant awn-shaped trichomes, 792 /*, for which reason the giant awn-shaped 

 trichomes ought probably to be considered a distinct type. 



The big-headed trichome is somewhat curved, so that it is frequently 

 closely appressed to the surface. In structure it is composed of a stalk of 

 2 cells and a head of an undetermined number of cells, probably 4. The 

 stalk-cells are hyaline; the cells composing the head are densely filled with 

 a coarse granular substance. These trichomes measure from 63 p to 75.6 p- 

 in length. 



SOLANUM GUINENSE, 



Two types of trichomes were observed in Solanum guinense, of which 

 one is glandular and similar to the big-headed trichome of Solanum villosum, 

 and the other is not glandular and is unlike any trichome seen in the other 

 species (fig. 3, e} . 



The trichomes were found mainly on the veins of the ventral surface of 

 young leaves and on young stems; the older stems and older leaves were 

 usually glabrous. 



The big-headed secreting trichomes were either straight or mostly curved 

 and appressed to the surface. They measure from 67 . 2 p to 71 .4 /* in length. 

 As in structure, size, and general appearance these trichomes are similar 

 to the analogous ones in Solanum villosum, a further description of them is 

 unnecessary. 



The non-secreting trichome (the uncommon type) is broadly awn-shaped, 

 is usually curved, and more or less closely appressed to the surface. It is 

 composed of 3 or 4 cells, which rest on a multicellular base. The trichomes 

 measure from 239.4 /* to 378.0 p- in length. 



SOLANUM VILLOSUM X SOLANUM GUINENSE. 



Two types of trichomes were observed in the hybrid Solanum. These 

 were in all respects like those of the species Solanum guinense, and conse- 

 quently were the big-headed secreting trichome and the awn-shaped non- 

 secreting trichome (fig. 3, e and/). The trichomes are on the ventral leaf- 

 surface, where they are confined to the veins. The big-headed trichomes 

 measure from 67.2 p- to 80 /* in length, and the awn-shaped trichomes from 

 252. 2 p. to 316.8 /* in length. 



The account above given is from a study of first-generation plants. 

 About a dozen second-generation plants were examined also and a condi- 

 tion quite like that observed in the first generation was found. Measure- 

 ments of the big-headed secreting trichomes of second-generation hybrids 

 showed that they ranged from 63.0 /* to 71.4 /* on the leaves, and 71.4 p to 



