150 
only determines which sort of sensation fur- 
nishes the common coin of his mental exchange. 
A person who is motor in this sense may or 
may not be more impulsive than a good visual- 
izer ; it all depends on whether his motor cues 
habitually bring with them contrary sugges- 
tions.. Experience seems to show that some of 
the most hesitating of us act from motor cues, 
while some of the most impulsive persons are 
of the ‘sensory’ and, indeed, of the visual type. 
We are hardly in a position, tWerefore, to hold 
out the hope that the ordinary type-tests will 
decide whether a boy needs encouragement in 
precipitateness or in hesitancy. Whether he is 
too cautious or too headlong is to be settled by 
observations ad hoc, and is not decided by dis- 
covering which sense furnishes the stuff of his 
mental imagery. 
But details of this sort to which objections 
might be raised are not many nor are they so 
important as to affect the general tone of the 
book. Asa whole it does admirable justice to 
the more fruitful lines of modern work and will 
be acceptable to the wide circle of persons 
who wish some intelligent guidance in psychol- 
ogy, without aiming to be students of it in the 
stricter sense. Even classes in psychology 
might well supplement their reading by a fresh 
narrative like this. And as for the poor school- 
teachers, accustomed to their juiceless ‘teach- 
ers’ psychologies,’ they will with difficulty be- 
lieve that a book which is really interesting can 
be the genuine thing. 
G. M. STRATTON. 
UNIVERSITY OF CALIFORNIA. 
How to Know the Ferns. By FRANCES THEODORA 
Parsons. New York, Charles Scribner’s 
Sons, 1899. 12mo. Pp. 215. Price, $1.50. 
When science has its cold matter of-fact 
angularities concealed by a certain amount of 
folk-lore, personal adventure and innocent 
poetical quotation the popular mind takes it in 
unwittingly without feeling the chilliness of the 
morsel, and if they are abraded by the angles, 
there is lubrication and mollification in the 
dressing that makes one forget the pain. The 
ordinary unscientific reader is shocked if told 
at once that an innocent looking fern is a 
Cystopteris, but when he is introduced to it as the 
SCIENCE. 
[N. 8. Von. X. No. 240. 
‘bulblet bladder-fern’ the added _ syllables 
cause him no uneasiness and it is quite a dif- 
ferent matter. All this softening of the rough 
angles of a scientific treatise is heightened if 
attractive illustration furnishes the ready op- 
portunity to save the often tedious work of 
identification through technical language. 
Such a happy combination we have presented 
in a most attractive form in the book before us. 
The popular interest is attracted by the per- 
sonal narratives and one forgets the personal 
pronouns; one forgets even the rather doubtful 
compliment paid to the main subject when one 
reads that ‘the greatest charm the ferns possess 
is that of their surroundings,’ a fact emphasized 
by the frontispiece where the pose of the hand- 
some young woman surely throws ‘the cheer- 
ful community of polypody’ quite into the 
shade, yet a more attractive picture could 
scarcely have been chosen. 
The work is well written and is really one 
that can scarcely do otherwise than interest 
many people who have neither the time nor the 
mental perseverance for severe study, in one of 
the most delightful of subjects, and it will cer- 
tainly bring many into a closer touch with 
Nature and her productions. The text is in the 
main very accurate, and the illustrations really 
illustrate the subject, and do it so well that one 
must be blind who cannot with their aid iden- 
tify the ferns of the Northern States. The 
drawings by Miss Satterlee with less of the im- 
pressionist touch appeal more strongly to the 
cold scientific eye, though all of them are well 
executed, and the full-page half tones are well 
chosen and excellent. 
While the authoress appears to us under a 
new name, we recognize in Mrs. Parsons the 
same writer that a few years ago as Mrs. Dana 
gave us the equally valuable book, ‘How to 
Know the Wild Flowers.’ Armed with these 
two, many who heretofore have had only 
guides that were too severe for their summer’s 
outing can be easily and delightfully introduced 
to the ferns as well as the flowers of the woods 
and fields. L. M. UNDERWOOD. — 
BOOKS RECEIVED. 
GEORGES TREILLE. 
1899: Pp. 272: 
Principes ad’ hygiene coloniale. 
Paris, Carré and C. Naud. 
