NOTES ON THE FORMS OF CASTELA GALAPAGEIA 
287 
Forma jacobensis Robinson 
Described as being armed with very short spines. Leaves broadly 
oblong entire, rounded at base and apex, mucronate, shiny above and 
transversely wrinkled, 1-1.8 cm. long. It can readily be seen that 
this description is very similar to that given for the form albemarlensis. 
The only essential difference between these two descriptions is that 
the leaves in albemarlensis are somewhat larger and are often furnished 
with one to two lateral teeth as shown in figure if. The presence of 
lateral teeth on the leaves is a rare character, however, as shown by 
the series of Academy specimens, and the size of the leaves varies 
greatly even on the same specimen. Spatulate leaves, and those which 
are lance-oblong in shape occur on the type mentioned. The shininess 
and wrinkled character of the leaves are not distinctive as mentioned 
above. 
From the above discussion it can be readily seen that characters 
based on the arming of the stem and the shape of the leaves are too 
inconstant to be used in establishing formal varieties, and unless more 
constant characters are found we must conclude that they do not 
exist in this species. We are of course dealing in such forms with 
groups of organisms very closely related to each other between which 
the differences are very slight. However small these differences may 
be, they must be constant, otherwise the supposed forms cease to 
exist and we have instead only a group of slightly dissimilar individuals. 
This species occurs most abundantly on the lower dryer parts of 
the islands, but it is not uncommon to find it at elevations from 
600 to 1,000 feet. It is well known that climatic conditions vary 
greatly within comparatively slight differences in elevations on these 
islands. The lower parts adjacent to the shore are very dry and sup- 
port a xerophytic vegetation while the upper parts varying usually 
from 500 to 1,000 or more feet in elevation are moist with a meso- 
phytic vegetation. Between these two there is usually an intermediate 
or transition region, covered with a vegetation which is made up for 
the most part of species from both the dry and moist region. Growing 
under such a variety of conditions as this we would naturally expect 
that the difference in environment would have a corresponding effect 
upon the habit and general appearance of this species, and such is the 
case. I believe, however, that the changes brought about by such 
causes in Castela are even less marked than in some of the other 
species of Galapagos plants which occur in like situations. 
