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 triehomes in Solanum villosum, 

 all of which are multicellular and glandular (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 triehomes. The triehomes 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 triehomes occurred between the veins; all were found on the 

 veins . 



V 



\ 



Pig. 3. Triehomes of Solanum pure species and hybrids. Solatium 

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

 It, giant awn-shaped secreting trichome from region of midrib, veu- 

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

 Solarium guinense: d, big-headed glandular triehomes from ventral 

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

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

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

 ehomes see text; reduced one-half.) 



The awn-shaped triehomes 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 granular matter. The stalk-cells are 

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

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

 loner. 



