532 Mutations 



served any trace of reversion to the lamarck- 

 iana type. I have also cultivated them in suc- 

 cessive generations with the same result. In 

 a former lecture we have seen that contrary to 

 the general run of horticultural belief, varieties 

 are as constant as the best species, if kept free 

 from hybrid admixtures. This is a general rule, 

 and the exceptions, or cases of atavism are ex- 

 tremely rare. In this respect it is of great inter- 

 est to observe that this constancy is not an ac- 

 quired quality, but is to be considered as innate, 

 because it is already fully developed at the very 

 moment when the original mutation takes place. 

 From its first leaves to the rosette period, 

 and through this to the lengthening of the stem, 

 the dwarfs are easily distinguished from any 

 other of their congeners. The most remarkable 

 feature is the shape of the leaves. They are 

 broader and shorter, and especially at the base 

 they are broadened in such a way as to become 

 apparently sessile. The stalk is very brittle, 

 and any rough treatment may cause the leaves 

 to break off. The young seedlings are 

 recognizable by the shape of the first two or 

 three leaves, and when more of them are pro- 

 duced, the rosettes become dense and strikingly 

 different from others. Later leaves are more 

 nearly like the parent-type, but the petioles re- 

 main short. The bases of the blades are fre- 



