MUTATION IN G@NOTHERA 147 
his facts, amounts to. De Vries made observations 
upon a large proportion of the plants of his district 
by the method of growing great numbers of their 
seedlings, but he failed to find the same phenomenon 
going on in any of them. He therefore supposes that 
species are subject to comparatively short periods of 
mutability which recur at relatively long intervals, 
and that all the species he examined except the 
Cnothera were in this intermediate stable period of 
their existence. Direct proof of this suggestion is 
naturally out of the question. 
It will be well to summarize briefly the conclusions 
at which de Vries has arrived, as the result of his 
observations upon Cnothera. 
The following are the points to which he attaches 
chief importance : 
i. The new species arise suddenly at a single step, 
without transitional forms. 
2. They are usually fully constant from the first 
moment of their origin. 
3. The distinctive characters of the new forms agree 
in kind with those which distinguish from one another 
such old and established species allied to Gnothera 
Lamarckiana as O. biennis and O. muricata. Only one 
of the new forms—namely, O. nanella, a dwarf type— 
is analogous with any ordinary kind of variety of 
garden origin. 
4. A considerable number of individuals of the same 
sort usually make their appearance at the same period. 
5. Although the new types vary in a normal fashion, 
and frequently transgress the limits dividing them 
1o—2 
