OcToBER 15, 1897.] 
While the practical results of the season’s 
work have been to more firmly strengthen 
the contentions of the United States, the 
scientific results have been more than ex- 
pected. The observations of Mr. Clark, 
while throwing much light on the problem 
of early starvation of young, have also done 
much to explain the manner in which ha- 
rems are formed and the massing of seals in 
particular spots when there is plenty of 
room and often better ground close at 
hand. 
The noticeable scarcity of three-year old 
females indicates the truth of the supposi- 
tion that the death rate is high, this being 
the only class whose abundance or scarcity 
could well be noted, owing to the great 
similarity in the appearance of the older 
seals. On only one point did the results of 
this year’s observations differ materially 
from those of last year, and this is in re- 
spect to the cause of death among young 
seals. The conclusion reached last year 
that the great majority of deaths among the 
pups was due to their being trampled on by 
the old seals is found to be erroneous and 
that the mortality is caused by a parasite, 
a species of Uncinaria, found in the small 
intestine. This course of danger was pointed 
out by Dr. Stiles as a result of the examina- 
tion of a very few specimens obtained in 
1896, and the matter will be discussed at 
length later. It may be said that young 
seals —and they alone seem to be affected— 
dying from an attack of Uncinaria perish so 
quickly that they lose little of their fat and 
that the disease is practically over before 
the end of August. 
Finally, the past summer was unusually 
dry and clear, these conditions greatly 
facilitating the work of the party from the 
U. S. Coast Survey which is engaged in 
making a careful survey of the islands and 
especially of the breeding grounds. 
1B5 Ake IDE 
SCIENCE. 
569 
A BOTANICAL EXCURSION TO MEXICO. 
Mexico is a profitable place for the 
botanist to visit on account of the rich- 
ness of the flora, numerically speaking, and 
because of the assemblage in one geo- 
graphical region of many species peculiar 
to a certain physical or meteorological zone. 
The aquatic flora, the Alpine flora, the 
desert and tropical floras, are all found as- 
sociated within a radius of a few miles. 
Altitude and the distribution of the rain- 
fall explain this somewhat interesting fea- 
ture of the flora. The problems presented 
to the botanist for solution are very in- 
tricate, and it is necessary for him in order 
to solve the more difficult questions to 
spend considerable time in the field where 
the plants are to be found surrounded by 
natural conditions. 
Each of the plant communities into 
which the flora of a country as vast as 
Mexico can be divided can be distin- 
guished by the component plants which, 
together by their collective features, give 
character to the vegetation of a particular 
meteorological, geological or physical re- 
gion of the earth’s surface. Such a flora 
as the Mexican can be classified into 
several ecological* communities, as follows : 
1. Hydrophytic Community, composed 
of Hydrophytes, or water-plants. 
2. Xerophytic Community, composed of 
Xerophytes, or desert-plants. 
3. Halophytic Community, composed of 
salt-loving plants. 
4, Mesophytic Community, including 
those plants found.in intermediate situa- 
tions, such as plants of the tropical forests, 
palm forests, bamboo thickets, temperate 
deciduous forests, subtropical evergreen 
forests and plants of the Arctic, Alpine and 
prairie regions. 
The valley of Mexico is especially suited 
* Ecology is the study of plants with reference to 
their environmental conditions and covers the field of 
the so-called biology of plants. 
