Rec. May 22 | Berlin April 24,1867 
Ans. Jun 18 Postmarked May 2 
My dear Engelmann ; 
I received your letter of Aptil 8 day before yesterday 
and want to answer immediately, even thoush I posted a letter to 
you some 8 days ago., which contained a complete oversieceht of the 
northamerican Isoetes as well as the desired news about I. flacc. 
Nutt. and Chapmanri. I hope that you will be satisfied with the 
major part of my inquiries, specially with the curious geogra - 
phical separation of I. echinosp. and ambigua. Most problematical 
are Il. paupercula and canadensis,which probably need further in- 
vestigation with better material, though both appear to be inter- 
esting Intermediate forms. The varieties of I. Engelmanni may also 
need another better look. Today are primarly the californian 
forms, about whos'e investigration I warnt eG communicate. You say 
that 3 items from 3 localities have been collected by Bolander, 
Unfortunately I received only 2 specimens from you and these do 
not entirely match with yours. You mention in the letter 5080, 5091 
and 5093; I received 5091 (the largest, looking likeechinosp.) 
and 6025 (the dwaf form). My number 5091 has many stomata which 
are easy to see. They appear specially strong as I added some 
tincture of iodine, which colors the boundary cells blue,while 
the other cells. doinbtäcontäimmanyistareh. "There is no doubt 
about this and you will find them surely if you check No. 5091 
again. I usually insert a flat,pointed point of a little krife 
into the side of a leaf and then slice lengthwise to the tip if 
successful,parting the leaf into 2 lamelles from which I try to 
scerape roushly the scaffold of the dividinz walls. One or two 
layers of parenchyma, which remain from the epidermis (most spe- 
cies do not have more)do not impede looking for the stomata, be- 
cause below every stomais a void inthe parenchyma layer. For I. 
9 MEREZel 
. BOTANICAL 
eloJe)liglelsimc-ti-1et7-Te GARDEN 
