370 L. F Ward — Fossil Dicotyledonous Leaves. 



Neuchatel, although not reported on until 1849, at the Cam- 

 bridge meeting of the American Association.* 



Guyot had been teaching at Neuchatel nine years when, 

 suddenly, the "Academy" was suppressed by the Grand revolu- 

 tionary Council at Geneva of 1848. The 13th of June brought 

 the tidings; and on the 30th, the end came " without any in- 

 demnity to the Professors." Letters from Agassiz urged Guyot 

 to come to America. Though reluctant to take the step 

 because of the many ties of friendship and association that 

 bound him to Switzerland, and especially on account of the 

 family under his charge (consisting of his mother, then 70 years 

 old, and two sisters), which he should have to leave behind, he 

 had the decision of his mother, after her careful reading of 

 Agassiz's letter, in favor of it ; and in the following August he 

 left friends, home, and Europe. 



Art. XXXIY. — On the Determination of Fossil Dicotyledonous 

 Leaves; by Lester F. Ward. 



Frail as mere leaves would seem to be as objects to be pre- 

 served in the rocks of the earth's crust, observation shows that 

 of all organs of vegetation they are the most numerous in the 

 plant-bearing beds of recent formations. The fact being known 

 the explanation is easy. The two chief conditions to preser- 

 vation are firmness of consistency and rapidity of deposition. 

 A large or thick body is longer in being covered up and in 

 order to escape decay before burial it must have firmness and 

 durability of structure proportionate to the time required. 

 Hence it is that fruits and twigs of any considerable thickness 

 are rarely found except in such formations as bear evidence of 

 having been suddenly or rapidly deposited, like travertines, 

 tufa-beds, etc. In beds of slow formation as a rule only leaves 

 are found. Those that give proofs of having been evergreen 

 are most numerous because of the firmer consistency of ever- 

 green leaves. But deciduous leaves also occur, partly perhaps 

 because the chances are increased by the greater number that 

 annually fall, and partly because thinner and more quickly 

 covered. We thus have, in many parts of the world, large de- 

 posits of dicotyledonous leaves ranging from the Cenomanian 

 to the Quaternary, in which no other organs are preserved. 



The great importance, therefore, of finding some characters 

 in these leaves which can be depended upon to reveal their 

 relationships becomes obvious, and this was early perceived. 



* Proc. Amer. Assoc, ii, 115. 



