Mendel's Experiments with Hieracium 97 



fertilisation without either letting pollen get on to the 

 stigma or injuring the pistil so that it withered away. 

 As is well known, the anthers are united to form a tube, 

 which closely embraces the pistil. As soon as the flower 

 opens, the stigma, already covered with pollen, protrudes. 

 In order to prevent self-fertilisation the anther-tube must 

 be taken out before the flower opens, and for this purpose 

 the bud must be slit up with a fine needle. If this 

 operation is attempted at a time when the pollen is mature, 

 which is the case two or three days before the flower opens, 

 it is seldom possible to prevent self-fertilisation: for with 

 every care it is not easily possible to prevent a few pollen 

 grains getting scattered and communicated to the stigma. 

 No better result has been obtained hitherto by removing 

 the anthers at an earlier stage of development. Before the 

 approach of maturity the tender pistil and stigma are ex- 

 ceedingly sensitive to injury, and even if they are not actually 

 injured, they generally wither and dry up after a little 

 time if deprived of their protecting investments. 1 hope 

 to obviate this last misfortune by placing the plants after 

 the operation for two or three days in the damp atmosphere 

 of a greenhouse. An experiment lately made with H. 

 Auricula treated in this way gave a good result. 



To indicate the object with which these fertilisation 

 experiments were undertaken. I venture to make some 

 preliminary remarks respecting the genus Hieracium. This 

 genus possesses such an extraordinary profusion of distinct 

 forms that no other genus of plants can compare with it. 

 Some of these forms are distinguished by special peculiarities 

 and may be taken as type-forms of species, while all the 

 rest represent intermediate and transitional forms by which 

 the type-forms are connected together. The difficulty in 

 the separation and delimitation of these forms has demanded 



B. 7 



