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



as to be mistaken for " thickened rhizomes devoid of definite tubers," or that 

 possibly the plants which Lindley examined may not have been fully developed, 

 in which case the tubers would not yet have been formed. 



The examples of Solanum etuberosum which I possess came originally from 

 the Botanic Gardens, Edinburgh, in March, 1887, through Mr. Lindsay, and a.i>ain 

 from the same stock in 1897 from Dr. Bayley Balfour. They produced at first 

 small tubers about the size of walnuts, and the calyces are hispid ; in other respects 

 the plants are similar to the type specimen described by Lindley. 



Solatium etuberosum has been grown continuously for more than twenty years 

 in the Trial Grounds at Reading. During that time no variation has occurred 

 in the characters of the foliage or flowers of the plants. The tubers have also 

 retained their original form and colour with the exception of an increase in size. 



Up to 1906 the plants had never been seen to bear fruits, but in that year a 

 single berry was found in the centre of the plantation and allowed to ripen. 

 Whether this was the product of self-fertilization or the result of a cross with 

 some other Solanum growing near, it is impossible to say. 



The seeds taken from this fruit were sown, and during the past season (1907) 

 twenty young plants were raised. None of these resemble the parent form very 

 closely, but they exhibit the same variation that is met with among seedlings 

 of the cultivated potato. 



The tubers of the parent Solanum etuberosum are white in the skin and flesh, 

 and after twenty years of garden culture average about \\ inches in diameter. 

 Those of the seedlings, however, vary very much in size, some being already as 

 large as cultivated potatoes : they are also very varied in colour of skin, some 

 being white, others dark purple, pale blue, or rose-white ; one seedling has given 

 tubers the flesh of which is deep purple and the skin almost black, characters 

 which are met with in some of the cultivated varieties now growing in Chile. 



The pollen-grains of the parent are elliptical like those of all wild species, and 

 the seed-berries are round or slightly oval, but are covered somewhat closely 

 with distinct white spots, in which they differ from the fruits of all other wild 

 types. 



(Plate 10. Solanum etuberosum, Lindl. White-flowered seedling.) I was 



only able to examine the pollen-grains of one of the twenty seedlings above referred 

 to, and that happened to be a plant bearing white flowers. In this case the pollen- 

 grains were regular and elliptical, and entirely similar in form to those of the 

 parent. 



N.B. In order to avoid any doubt as to the parentage of the seedlings above 

 described, several different blooms of Solanum etuberosum were artificially sclf- 

 pollinated under controlled conditions in 1907. Ripe fruits were obtained from 

 several flowers. Seedlings raised from these in 1908 exhibit the same variability 

 in character of foliage and colour of the flowers as those obtained from the single 

 berry collected in 1906, the male parent of which was uncertain, and they vary 

 also in the form and colour of tuber. 



Some of the plants raised from the same berry have white flowers, others lilac- 

 coloured blooms. 



