Wild Forms and Species of Tuber-bearing- Solanums. 3 



(Plate 8. Solanum tuberosum,, Linn., var.) The chief points of interest in this 

 plate are : 



(a) The regular and elliptical form of pollen-grains. 



(6) The wheel-shaped corolla, in contrast with the star-shaped corolla of 

 'Solanum Commersonii (Plate 5). This wheel-shaped corolla is also seen 

 in Solanum Maglia (Plate 1), in Solanum etuberosum (Plate 9), and almost 

 universally in the cultivated potatoes. 



(c) The round form of the seed-berry, in contrast with the cordiform seed- 

 berries of Solanum Commersonii (Plate 2). 



2. Solanum polyadenium, Greenman, also from Mr. Stuart. This species is one 

 of the most distinct of all wild tuber-bearing Solanums with which I am acquainted, 

 the leaves and stems being covered with a dense coat of hairs, and emitting a 

 strong scent somewhat resembling that of Feverfew, Pyrethrum Parthenium, Sm. 



3. Solanum verrucosum, Schlecht. ' 



4. Solanum tuberosum, var. boreale ( Solanum Fendleri, A. Gray), from Arizona. 

 The latter was sent to me by the Rev. J. Aikman Paton, of Castle Kennedy, 



Scotland. 



5. Solanum etuberosum, Lindley. (Plate 9.) 



The five last mentioned wild species, except Solanum etuberosum, flower 

 freely, and produce fruits containing an abundance of seeds. The plants raised 

 from seed of these wild species (excepting only Solanum etuberosum} exhibit no 

 variation whatever from the parents or among themselves, even when the seeds 

 are taken from plants allowed to flower in close proximity to other species. 

 Seedlings, however, of the commonly cultivated potatoes differ very widely from 

 each other, those raised from the seed-berry or fruit generally exhibiting extensive 

 variation in foliage, colour of tuber, and in habit of growth. 



I find that the pollen-grains of all these wild species are of one particular shape, 

 namely oval or elliptical, whereas the pollen-grains of all the cultivated potatoes 

 which I have examined are very irregular in form and size, and possibly degenerate. 

 This fact is clearly illustrated on Plate 12. 



One of the forms or species which has proved of great interest, and which on 

 account of its remarkable exemption from disease may become of economic value, 

 is Solanum etuberosum, Lindley. This name was given by Lindley in 1834 to a 

 tuberless Solanum, which he states was obtained from Chile some years previously 

 by the Horticultural Society. He described it as exceedingly like the ordinary 

 potato, Solanum tuberosum, Linn., in all its characters, except that it possesses 

 thickened rhizomes devoid of definite tubers, and the calyx and flower-stalks are 

 smooth instead of hairy. 



It may be remarked here that if Lindley's plant of Solanum etuberosum produced 

 no tubers, it would have been difficult to propagate it except from seed ; and 

 judging by the behaviour of the plants I have experimented with, it is not likely 

 that Lindley's plants reproduced themselves from seed, for two reasons : 1st, 

 that seed-berries are very rarely formed, and 2nd, when formed the seedlings 

 resulting therefrom differ so markedly from the parent stock. It may be suggested 

 that the Solanum etuberosum when growing in the wild state, the tubers, of course, 

 not being lifted from year to year and replanted, might produce tubers so small 



