160 PISUM SATIVUM. CHAP. V 



lots of seeds in poor soil in a shady place in a shrubbery. Here 

 again the self-fertilised' plants from the self-fertilised for a long 

 time exceeded considerably in height those from the previously 

 crossed plants; and this may probably be attributed, in the 

 present as in the last case, to these seeds having germinated 

 rather sooner than those from the crossed plants ; but at the 

 close of the season the tallest of the self-fertilised plants from 

 the crossed plants was 30 inches, whilst the tallest of the self- 

 fertilised from the self-fertilised was 29f inches in height. 



From the various facts now given we see that plants derived 

 from a cross between two varieties of the sweet-pea, which differ 

 in no respect except in the colour of their flowers, exceed 

 considerably in height the offspring from self-fertilised plants, 

 both in the first and second generations. The crossed plants 

 also transmit their superiority in height and vigour to their 

 self-fertilised offspring. 



PISUM SATIVUM. 



The common pea is perfectly fertile when its flowers are pro- 

 tected from the visits of insects; I ascertained this with two or 

 three different varieties, as did Dr. Ogle with another. But the 

 flowers are likewise adapted for cross-fertilisation; Mr. Farrer 

 specifies * the following points, namely : " The open blossom dis- 

 playing itself in the most attractive and convenient position for 

 insects ; the conspicuous vexillum ; the wings forming an alight- 

 ing place; the attachment of the wings to the keel, by which 

 any body pressing on the former must press down the latter ; 

 the staminal tube enclosing nectar, and affording by means of its 

 partially free stamen with apertures on each side of its base an 

 open passage to an insect seeking the nectar; the moist and 

 sticky pollen placed just where it will be swept out of the apex 

 of the keel against the entering insect ; the stiff elastic style so 

 placed that on a pressure being applied to the keel it will be 

 pushed upwards out of the keel ; the hairs on the style placed 

 on that side of the style only on which there is space for the 

 pollen, and in such a direction as to sweep it out; and the 

 stigma so placed as to meet an entering insect, all these 

 become correlated parts of one elaborate mechanism, if we 



* 'Nature,' Oct. 10, 1872, p. description of the flowers, 

 479. H. Muller gives an elaborate fruchtung,' &c. p. 247. 



