452 MR. C. DARWIN ON SPECIFIC DIFFERENCES IN PRIMULA. 



that it was a strange variety of V.tha^sus. It attained the height 

 (by measurement) of 8 feet ! It was covered Avith a net ; and most 

 species of Verhasciim, when thus treated, seed freely. Ten flowers 

 were also carefully fertilized with pollen from the same plant ; 

 and later in the season, when uncovered, it was freely visited by 

 bees ; nevertheless, although many capsules were produced, not 

 one contained a single seed. During the following year this same 

 plant was left uncovered near plants of V, tJiapsiis and lyclinitis] 

 but again it did not produce a single seed. Pour flowers, how- 

 ever, which were repeatedly fertilized whilst the plant was under 

 the net with pollen of F. lychnitis^ produced four capsules, which 

 contained five, one, two, and two seeds \ at the same time three 

 flowers were fertilized with pollen of V, tJtapsus, and these pro- 



r 



duced two, two, and three seeds. To show how unproductive 

 these eight capsules were, I may state that a fine capsule from 

 a plant of V. thapsus growing close by contained above 700 

 seeds. These facts led me to search the moderate-sized field 

 whence the plant had been removed, and I found in it many 

 plants of V. thapsus and lychnitis and of no other species, and 

 thirty-three plants intermediate in character between these two 

 species. These thirty-three plants differed much from each other. 

 In the branching of the stem they more closely resembled V. lych- 

 nitis tlian V. thapsus^ but in height the latter species. In the 

 shape of tlicir leaves they often closely approached V. lychnitis, but 

 some had leaves extremely woolly on the upper surface and decur- 

 rent like those of 7^. thapsus -, yet the degree of woolliness and of 

 decurrency did^not always go together. In the petals being flat 

 and remaining open, and in the manner in which the anthers of 

 the longer stamens were attached to the filaments, these plants 

 all took more after V. lychnitis than V. thapsus. In the yellow 

 colour of the corolla they all resembled the latter species. On the 

 whole, these plants appeared to take rather more after V. lychnitis 

 than V, thapsus. On the supposition that they are hybrids, it is 

 not an anomalous circumstance that they all should have produced 

 yellow flow^ers ; for Gartner crossed white- and yellow-flowered 

 varieties of Verhascum^ and the off'spring thus produced never 

 bore flowers of an intermediate tint, but either pure-white or pure- 

 yellow flowers, generally of the latter colour *. 



My observations were made in the autumn ; so that I was 

 able to collect some half-matured capsules from twenty of the 

 thirty-three intermediate plants, and likewise capsules of the pure 



* Bastarderzeugiing, p. 307. 



