72 FERN GROWING 



white (in two of the trials none were white), with equal parts of 

 pollen (red and white) ; using two parts of white pollen to one 

 of red did not appreciably alter the result — though crossed with 

 a white flower very few were white ; but with six parts white 

 to one of red a large proportion of white seedlings was raised. 

 When this single dahlia was first introduced, Professor 

 Lawson (then director of the Oxford Botanic Gardens) gave 

 Mr. Joseph Sidebotham, of Manchester, seeds which produced 

 both white and red flowers. Mr. Sidebotham presented to the 

 author seeds of the white variety (called Stella bianco), but 

 they did not produce even one white seedling. In the follow- 

 ing year the author had a division of the white variety, and, 

 whilst isolated, the whole of its seedlings were white. Bees 

 fly from flower to flower, and thus the pollen becomes 

 mixed ; but if only one sperm effected impregnation, we should 

 raise white flowering seedlings abundantly. 



There appears no doubt that when impregnation has 

 taken place no second contact of pollen will have any effect ; 

 care is only required so as to be enabled to accomplish the 

 first contact ; after this, insects cannot produce any change. 



It requires isolation to raise plants like the parent. If 

 we instance the white variety of Agrostemma coronaria, under 

 these circumstances the seedlings will be white. Aquilegia 

 glandulosa, if away from all other Aquilegias, will produce 

 plants like the parent ; but if the English Aquilegia vulgaris 

 is near, a combination results, and in two or three years 

 there will not be a single plant raised that is true Aquilegia 

 glandulosa. It is the same with other plants that freely 

 cross. From this cause it is now difficult to raise true plants 

 of Cupressus Lawsoniana. Papaver alpina growing near 

 Papaver niidicaule is soon lost, and a mixture of the two 

 becomes established. This was known years ago both by Mr. 

 Henderson, of Wentworth, and Mr. Elworthy, of Nettlecombe 

 Court, and both kept Papaver alpina isolated, and thus preserved 



