. 4 . 
that for instance with ambigua 2, 3 or more systems of spines com- 
bine to form a ridge (could bescomb,E.D.). Why should not more fuse 
and the ridres join to form nets in the end ? I have alreadv shown 
on several forms of ambigua that the stomata are not a reliable poin# 
of reference; for others you yourself have Br ernined this. Color, 
form, size of leaves are so changeable, specially with ambigeua, that 
not much weisht can be given to them; the lisht-green,longe-leaved 
form from the Catskill,Mansfield etc. represents thus a complete 
transition to muricata .- The case of the form of the tubers, as Il 
have seen so often, is such, that I have given up to make them part 
of my diagnosis. Specially so for ours during Summer when their form 
changes from"flat to round and turnip-like through the pushing-off 
of the growth of the preceding year. Soma Engelm. I believe I have 
sent youU,- 
And now you berin to doubt even the vascular bundles. It appeared 
to me that they were not easy to find in the hard middle-leaves of 
Engelm, thonush these are immature leaves that should not count, but 
only the mature ones,- The size of the velum is also not constant. 
If you should enumerate canadersis as a species, even as donbt- 
ful, then I am sorry I sent it to you. I have told you,that I receiv ed 
Wi 
good, ripe Braunii and riparia from Canada, but I do not find stomata 
in the latter,just as you, but do find sclerenchyma cells,microspores 
o 
laree as in riparia 0.032-0.036, macrospores 0.42-0.57 mm but in/ poor 
shape to examine them otherwise; I consider them a form of riparia. 
Thus the ambiprua is distinguished through very large spores; leaves 
thick and 10-14 cm long;the spores 0.40-0.46 mm diameter, 
I.ambireua is entirely your species as I have absolutely no clain; 
If the name Braunii must be eliminadted on account of the tertiary nane- 
cousin, then ambigcua remains your name, If it is recornized as a valid 
species.- then howeter it ercompasses probably muricata and BoottiF.- 
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