14 



HEREDITY AS ILLUSTRATED BY TRICHOMES. 



TRICHOMES OF SOLANUM VILLOSUM X SOLANUM GUINENSE 

 AND OF THE PURE SPECIES. 



SOLANUM VILLOSUM. 



There are 2, or possibly 3, kinds of trichomes in Solanum villosum, 

 all of which are multicellular and grlandular (fig. 3, a, b, and c). These 

 for convenience are in this paper called the awn-shaped, the giant awn- 

 shaped, and the big-headed trichomes. The trichomes were observed on 

 the stem, on the lobes of the calyx, and on the ventral surface of the leaves. 

 On the stem and on the calyx all 3 types occurred, with no apparent 

 choice of position, but on the leaf the distribution was as follows: only the 

 awn-shaped trichomes occurred between the veins; all were found on the 

 veins . 



Fie, 3.— Trichomes of Solanum pure species and hybrids. Solanum 

 villosum: a, awn-shaped secreting triohome from leaf, region of vein; 

 6, giant awn-shaped secreting trichome from region of midrib, ven- 

 tral leaf-surface; c, big-headed glandular trichomes from young stem. 

 Solanum guinense: d, big-headed glandular trichomes from ventral 

 leaf-surface; e, awn-shaped non-secreting trichome. Solanum villo- 

 sum X 8. guinense: f, big-headed glandular trichome from ventral 

 surface of leaf; g, big-headed glandular trichome. (For size of tri- 

 chomes see text; reduced one-half. ) 



The awn-shaped trichomes are composed of a single row of cells, usually 

 5, which constitute the stalk, and a single terminal cell, which is some- 

 what swollen and contains coarsely .eranular matter. The stalk -cells are 

 provided with a delicate protoplasmic lining and are hyaline. They meas- 

 ure from 176/". to 352/^ in length, with the greatest number about 193/* 

 long. 



