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 p- 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 p-, 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 appresscd 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 h- to 75.6 M 



in length. 



SOLANUM GUINENSE. 



Two types of trichomes were observed in Solatium 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 mostlv curved 

 and appressed to the surface. They measure from 67. 2 c- to 71 A ^ 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 p to 378.0 / 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 gniiiense, 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 f- to 80 /* in length, and the a\vn-shaped trichomes from 

 252.2 Mo 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 M to 71.4 p on the leaves, and 71.4 /n to 



