CHAP. II. SUMMARY OF OBSERVATIONS. 51 



from a distinct stock, and the seedlings thus raised may be 

 called the Colchester-crossed great-grandchildren. In my anxiety 

 to see what the result would be, I unfortunately planted the 

 three lots of seeds (after they had germinated on sand) in the 

 hothouse in the middle of winter, and in consequence of this the 

 seedlings (twenty in number of each kind) became very unhealthy, 

 some growing only a few inches in height, and very few to their 

 proper height. The result, therefore, cannot be fully trusted ; 

 and it would be useless to give the measurements in detail. In 

 order to Strike as fair an average as possible, I first excluded all 

 the plants under 50 inches in height, thus rejecting all the most 

 unhealthy plants. The six self-fertilised thus left were on an 

 average 66 '86 inches high; the eight intercrossed plants 63 '2 

 high; and the seven Colchester-crossed 65 '37 high; so that 

 there was not much difference between the three sets, the self- 

 fertilised plants having a slight advantage. Nor was there any 

 great difference when only the plants under 36 inches in height 

 were excluded. Nor again when all the plants, however much 

 dwarfed and unhealthy, were included. In this latter case the 

 Colchester-crossed gave the lowest average of all ; and if these 

 plants had been in any marked manner superior to the other 

 two lots, as from my former experience I fully expected they 

 would have been, I cannot but think that some vestige of such 

 superiority would have been evident, notwithstanding the very 

 unhealthy condition of most of the plants. No advantage, as far 

 as we can judge, was derived from intercrossing two of the 

 grandchildren of Hero, any more than when two of the children ' 

 were crossed. It appears therefore that Hero and its descendants 

 have varied from the common type, not only in acquiring great 

 power of growth, and increased fertility when subjected to self- 

 fertilisation, but in not profiting from a cross with a distinct 

 stock ; and this latter fact, if trustworthy, is a unique case, as 

 far as I have observed in all my experiments. 



Summary on the Growth, Vigour, and Fertility of the 

 successive Generations of the crossed and self-fertilised 

 Plants of Ipomcea purpurea, together with some miscel- 

 laneous Observations. 



In the followi ag table, No. XVII., we see the average 

 or mean heights of the ten successive generations of 

 the intercrossed and self-fertilised plants, grown in 



E 2 



