CHAP. IX. SELF-STERILE PLANTS. 341 



found a trace of a similar difference with Corydalis 

 cava, as did Fritz Miiller with an Oncidium.* 



In considering the several cases above given of 

 complete or almost complete self-sterility, we are first 

 struck with their wide distribution throughout the 

 vegetable kingdom. Their number is not at present 

 large, for they can be discovered only by protecting 

 plants from insects and then fertilising them with 

 pollen from another plant of the same species and with 

 their own pollen ; and the latter must be proved to 

 be in an efficient state by other trials. Unless all 

 this be done, it is impossible to know whether their 

 self-sterility may not be due to the male or female 

 reproductive organs, or to both, having been affected 

 by changed conditions of life. As in the course of my 

 experiments I have found three new cases, and as Fritz 

 Muller has observed indications of several others, it is 

 probable that they will hereafter be proved to be far 

 from rare.f 



As with plants of the same species and parentage, 

 some individuals are self-sterile and others self-fertile, 

 o which fact Reseda odorata offers the most striking 

 instances, it is not at all surprising that species of 

 the same genus differ in this same manner. Thus 

 Verbascum phceniceum and nigrum are self- sterile, whilst 

 V. thapsus and lychnitis are quite self-fertile, as I 

 know by trial. There is the same difference between 

 some of the species of Papaver, Corydalis, and of other 

 genera. Nevertheless, the tendency to self-sterility 

 certainly runs to a certain extent in groups, as we see 



* ' Var. under Dom.' chap. auratum, Impatient pallida and 



xvii. 2nd edit. vol. ii. pp. 113-115. fulva, cannot be fertilised with 



t Mr. Wilder, the editor of a their own pollen. Bimpan shows 



horticultural journal in the U. that rye is probably sterile with 



btates (quoted in ' Gard. Chron.' its own pollen. 

 1868, p. 1286) states that Lilium 



