254 Gates.—A Systematic Analytical Study of 
The term variety has been used in many senses, and it has therefore 
seemed desirable to draw a distinction between two classes of varieties, 
although it is not always possible to distinguish clearly between them. The 
sharply defined variety or varietas abrupta (written var. abr.) is the term 
used to designate those forms which differ from the type in an abrupt and 
clearly defined manner, suggesting that they have arisen from the type through 
a mutation and exhibit a unit-character difference. On the other hand, 
varieties which exhibit a series of intermediate stages are known as transi¬ 
tional varieties ( varietas transitionis , written var. trans). Although it is 
not possible to classify all varieties in this way, yet it is deemed useful to 
make this distinction in certain cases. 
The original paper contains a mass of detail, so that only a few selected 
cases illustrating the point of view can be considered here. 
The genus Clintonia contains six species—two in eastern and two in 
western North America, one in Japan and eastern Siberia, and one in the 
Himalayas. They are all well-marked species. The differences between 
C. borealis and C. umbellulata in eastern Canada and the United States 
have been considered elsewhere . 1 These two species are the most closely 
related, differing chiefly in size and number of flowers and the pubescence 
of the pedicels. There has been relatively little extinction between them, 
and the steps by which they have diverged have been relatively small. Of 
the two western species, C . uniflora was probably developed from the 
ancestors of C. borealis through a few steps, chiefly retrogressive, in the 
production of a single white flower. 
The other western species, C. Andrewsiaua, must have attained its 
present condition through several well-marked progressive steps: (i) great 
increase in size, (2) increase in number of flowers, (3) change in flower-colour 
to rose. All these changes could not have resulted from a single mutation, 
and hence a considerable amount of extinction must have taken place. A 
difficulty arises here, for while a stouter mutation might be supposed to 
triumph over a less robust original condition, yet there is no obvious reason 
why rose-coloured flowers should replace yellow ones. Breeding experi¬ 
ments and a cytological examination of the four species would help to 
answer such questions as these. 
In forma lateralis , Peck, of the eastern C. borealis there are one or two 
lateral umbels on the scape, in addition to the terminal one. It is significant 
that this tendency in C. borealis is fully expressed in the constantly numerous 
lateral flower fascicles of C. Andrewsiana. 
In Smilacina the two eastern species have corresponding western 
varieties, respectively N. racemosa var. trans. aniplexicaulis and N. stellata 
var. trans. sessilifolia . Although in the east these two species are relatively 
fixed and uniform, yet their western varieties show all intergrades to the 
1 On Pairs of Species. Bot. Gaz., vol. lxi, 1916, p. 181, Figs. 2, 3. 
