as proof or not of Alternating Seasons. 395 
The results thus far show that exogenous plants, e. g., the 
orange and lemon, so placed, form growth-rings as regularly as 
do the forest trees. 
It would be interesting to know how generally exogenous 
plants in tropical regions exhibit these markings, an er 
they are annual or whether they are made at longer or at 
shorter intervals. I esi: found it difficult to obtain any in- 
formation on this point, either from books or from botanists. 
nual layers. There is a woody Phytolacca which makes more 
layers, at least twice as many, as it is years old—probably indi- 
cating two periods of growth and rest.” To this I add that 
there now lies before’me a section of Chenopodium aibum cut 
on the first of August, and consequently not more than four 
months old, in which are eight well defined rings. This section 
is as hard and compact and as well formed wood as if it were 
a section of ash or pine. 
n the other hand there are exogens growing even in this 
ese which, notwithstanding our cold winters and hot sum- 
, show not the slightest trace of a ring. I have before me 
a a section of Akebia quinquefolia cut by Dr. O. R. Willis on his 
wn lawn from a plant five years old, which has no such mark- 
tet Then from a little further south I have a section of the 
Passion Vine in the same condition; also one of the Iron Wood 
ip sie precip neh which presents — ne ssible traces 
ese also I am indebte . Willis 
‘Mise C. C. Haskell, of Vassar College, pee the result of her 
examination of the ‘tropical woods in their museum, as fol- 
lows: In the Moria atiara of the Amazon, the circles are very 
apparent. In the Aliso or Birch of the Indus, the circles are 
evident. They are seen, too, in the Brazilian Red-wood (Upper 
Amazon), and in Siphonia elastica or Rubber trée, as well as 
in the Moria peranya of the Rio or None are seen in the 
Tortoise Shell Wood or in the Cow 
These suffice to show that, in the sendin warm climate of 
the tropics, singe are formed as regularly as in the trees of our 
northern forests. But it may be said that although there is in 
these regions no Waernadion of hot and cold seasons, » yet that 
they do “undergo semi-annual changes from wet to. 
seasonless condition which a perpendicular axis would produce. 
But there is evidence that exogenous trees would form these 
