THE MUTATION FACTOR IN EVOLUTION 283 
rete seat upon the question of mutations, confining his atten- 
noth i i 
group that most of the crucial questions concerning mutations 
ei been debated and decided. 
ae careful investigations—not only of the external 
eseteeet characters of the various species, varieties, and 
mutations, but also of their cytology—lend weight to his con- 
with impatience the dogmatic utterances and limited views which 
have in certain quarters been impressed upon them, will welcome 
the more philosophical treatment and broader view which he has 
adopted. ne rool among his conclusions is the statement that 
mutation is not merely a phenomenon of hybridism but a process 
Sut generis, a conception which the author regards as amply 
justified; “every line of investigation of the Cinothera muta- 
tions,” he Says, “has strengthened this view, to the point of 
demonstration.” 
The book should interest every botanist who is anxious to 
keep in line with the trend of modern investigation, but it is of - 
Special interest to the systematist. The author has saretille 
di 
e 
pre-Linnean botanists. On this historical portion of his work 
much light has been thrown by the study of the old collections at 
the British Museum and at Oxford. Dr. Gates recognizes twenty- 
oe species, and gives a useful map indicating their distribution 
in North Americ 
It is evident that the progress of civilization has pret camel 
affected the original distribution of the species. t only hav 
several of them become widely distributed and comfortably Lettled 
in the Old World, but others have become rare or entirely lost 
in their original habitat. It is only recently that Gnothera 
amarckiana, as to the origin of which so much has been written, 
nes been discovered to have had a wild habitat. It is the common 
evening primrose of English gardens, and has been extensively 
naturalized on the Lancashire coast for more than a century, and 
is now known only naturalized and in cultivation. It has been 
from seed sent by Michaux from North America; rae recog- 
nized this species as different from the grandiflora of Solander, 
which had been introduced from Alabama, and changed the name 
to Gi. Lamarckiana. How the oat reached the Lancashire 
Pp. 
reproduces, probably represents this form. 
