The Mutatiofis in the Lamarckiana-Family. 237 



garded by most authorities as a variety; and this is es- 

 pecially the case with dwarf forms, which are known for 

 a whole series of species, and attain only half or less of 

 the stature of the species to which they belong. 



On this ground O. nanella may be regarded as a 

 variety; but it must not be forgotten that, from the 

 experimental point of view, it is just as good an element- 

 aiy species as those which we have described already.^ 



The dwarfs are, perhaps with the exception of 0. 

 lata, the easiest to recognize in my cultures. They ap- 

 peared annually, in every culture, except the smaller ones. 

 Among the 50,000 individuals which composed the whole 

 Lamar ckiana-idirmXy , 1 58 were nanella ; that is about 

 0.3%, a proportion which was remarkably constant in 

 successive years. 



The dwarfs can be easily and certainly recognized 

 during the whole course of their development. If grown 

 far apart and well lighted they are recognizable as soon 

 as the second leaf appears; the first leaf is, at that time, 

 broad with a broad almost heart-shaped base closely set 

 on its short petiole. In 1897 I identified and recorded 

 them by this character. Plants about which there was 

 the slightest doubt were allowed to develop further. 



The broad stumpy leaves are succeeded by one or 

 two lozenge-shaped ones with long stalks ; and the plant 

 looks as if it were reverting to O. Lamarckiaiia. This 

 however is not the case, for there soon follow a number 

 of very broad leaves, with very short petioles, closely 

 crowded together; with the result that the highly char- 

 acteristic dwarf rosette is formed. The way I dealt 

 with these plants in 1896 was to plant them out after 



^Jordan, {De Torigine dcs orhrcs fruitiers, 1853) has pointed 

 out that varieties are only a special form of elementary species. 



