51 6 THE AMERICAN NATURALIST.  [Vor. XXXIX. 
Myricacez, Cornacez, and Sapindacex. There is thus a very 
strong suggestion (1) that the Salicacez is in no sense a primi- 
tive family from the standpoint of geological succession, and (2) 
it is, as a whole, much more characteristic of the Tertiary than 
of the Cretaceous, more especially as a closer analysis of the 
one hundred and forty-one known species shows that this rule 
applies to each of the constituent genera as well as to the entire 
family, though more conspicuously to the genus Populus than to 
Salix. Thus we find that the forty-seven Cretaceous species 
embrace 34 of Populus and 23 of Salix, while the eighty-four 
Tertiary species embrace 59 of Populus and 25 of Salix, making . 
the ratio of Cretaceous to Tertiary 1:1.75 for the former and 
1: 1.09 for the latter — ratios which tend to indicate that these two 
genera and so the family as a whole, were in process of develop- 
ment even in Tertiary time, a conclusion which is in apparent 
accord with the recent origin of the family. 
Comparison of Cretaceous and Tertiary Floras. 
Seq. 3 Cretaceous | Tertiary 
No. Ratio. No. Percent. No. Percent. 
Proteacex I 19 : 0.00 19 1.09 0.00 0,00 
Menispermacex 2 17 : 0.00 1j 0.98 0.00 0.00 
Araliacex 3 6:000 — 5D 2 0 0.00 — 
Euphorbiacex 4 2 : 0.00 2 0.11 0.00 0.00 
Passifloracex 5 I : 0.00 I 0.06 0.00 0.00 
Asclepiadacee 5 I : 0.00 I 0.06 0.00 0.00 
Myoporinex 5 I : 0.00 I 0.06 0.00 0.00 
Convolvulacee 5 I : 0.00 I 0.06 0.00 0.00 
Bromeliacee 5 I : 0.00 I 0.06 0.00 0.00 
Casuarinex 5 I : 0.00 I 0.06 0.00 eoe 
Sterculiacex 6 [tolg 15 086 a 9H 
Myrsineze 7 Li ois 6 0.34 I 0.06 
Myrtacex 8 1:0.18 II 0.63 3 9H 
Hamamelacex 9 [:035 4 0.22 I 0.06 
Magnoliacex 10 1: 0,31 45 2.60 20 1.15 
Thymeleacex II 1:00,33 3 0.17 I 0.06 
Anonacee 11 FIG 3 0.17 I 0.06 
Araliacex 12 I : 0.36 47 2.71 17 o.98 
Sapotacex 13 I : 0.50 à 022 2 0.11 
Lauracex 14 1:056. © — 308 39. r 
Vitacex 15 1:06. 36 105 16 0.92 
