CHAP. III. CALCEOLARIA. 87 



The average height of the flower-stems on the twenty-five 

 crossed plants in all the pots taken together is 43 12 inches, and 

 that of the twenty-five self-fertilised plants 39 '82, or as 100 to 

 U2. In order to test this result, the plants planted in pairs in 

 Pots I. to VIII. were considered by themselves, and the average 

 height of the sixteen crossed plants is here 44 9, and that of the 

 sixteen self-fertilised plants 42'03, or as 100 to 94. Again, the 

 plants raised from the thickly sown seed in Pots XI. and X., 

 which were subjected to very severe mutual competition, were 

 taken by themselves, and the average height of the nine crossed 

 plants is 39 86, and that of the nine self-fertilised plants 35 ' 88, or 

 as 100 to 90. The plants in these two latter pots (IX. and X.), 

 after being measured, were cut down close to the ground and 

 weighed: the nine crossed plants weighed 57 '66 ounces, and 

 the nine self-fertilised plants 45 '25 ounces, or as 100 to 78. On 

 the whole we may conclude, especially from the evidence of 

 weight, that seedlings from a cross between flowers on the same 

 plant have a decided, though not great, advantage over those 

 from flowers fertilised with their own pollen, more especially 

 in the case of the plants subjected to severe mutual competition. 

 But the advantage is much less than that exhibited by the 

 crossed offspring of distinct plants, for these exceeded the self- 

 fertilised plants in height as 100 to 70, and in the number of 

 flower-stems as 100 to 48. Digitalis thus differs from Ipomcea, 

 and almost -certainly from Mimulus, as with these two species 

 a cross between flowers on the same plant did no good. 



CALCEOLARIA. 



A bushy greenhouse variety, with yettow flowers blotched with purple. 



The flowers in this genus are constructed so as to favour or 

 almost ensure cross-fertilisation;* and Mr. Anderson remarks t 

 that extreme care is necessary to exclude insects in order to 

 preserve any kind true. He adds the interesting statement, that 

 when the corolla is cut quite away, insects, as far as he has seen, 

 never discover or visit the flowers. This plant is, however, self- 

 fertile if insects are excluded. So few experiments were 

 made by me, that they are hardly worth giving. Crossed and 

 self-fertilised seeds were sown on opposite sides of a pot, and 



* Hildebrand, as quoted by t ' Gardeners' Chronicle,' 185H 



H. Miiller, ' Die Befruchtung p. 534. 

 der Blumen,' 1873, p. 277. 



