Vor. IJ STEWART—BOTANY OF THE GALAPAGOS ISLANDS 235 
these animals are large and unable to swim, they are able to 
keep afloat for a considerable time, long enough to float them 
from the mainland to the islands if we assume that the ocean 
currents were as strong and had the same general trend in past 
geological times as they have now. The ability that these 
animals have of living without food for a considerable time 
greatly strengthens this view. During our homeward voyage 
from the islands, in the autumn of 1906, our live specimens of 
tortoises went for over a month without food, a time suffi- 
ciently long, under favorable conditions, to float an individual 
from the mainland of North America to the islands, if one 
should happen to get adrift. It would not be absolutely neces- 
sary that both male and female tortoises should be introduced 
on the islands to start the race, for this could be accomplished 
if a single female specimen containing fertilized eggs should 
be cast upon the shores of the islands. 
Turning to the botanical side of the question, we would natu- 
rally expect that of the eighty families of vascular plants found 
on the islands some few at least would have approximately the 
same number of genera and species as are found in these same 
families on the mainland. The following table shows all of 
the families of vascular plants which contain ten or more 
species, varieties, forms, and indeterminate species. 
FAMILIES OF GALAPAGOS PLANTS WITH TEN OR MORE SPECIES, 
VARIETIES, OR FORMS 
No. of Species, 
Rank Family Nasi ves 2 and |Indeterminate] Total 
1 IBICES Fe teh Seles he oe 77 agi 
he Gompositaeven Ae as las te ae 65 4 69 
3 Baphorbiaceae ss. 245 cite ee 50 10 60 
+ Gramineae... eases sep ses eons 49 6 55 
5 Wecuiminosaes 6.20: oisiseis be. 45 8 53 
6 AMArTanbAaceae sh yates 33 33 
7 (Cy peraceas snr. mers anon « Ds 3 28 
8 NOIATIACEAG ).524.5 155 dhe ans: 19 7 26 
9 RADIACEHE as Lene cee 22 1 23 
10 NMialvaceade saree rane paseke 19 3 22 
11 Boraginaceae 2.4/2.5 sas. eek: 20 1 21 
12 Convolyulacedes 2 i jact. 15 15 
13 Werpenaceae si hiss, eens a 13 2 15 
