1886. | BOTANICAL GAZETTE. 303 
that the two leaves of the latter are the representatives of the one in P. mo- 
nophylla can not be held for a moment. If, therefore, P, monophylla and P. 
edulis intergrade it can only be on the supposition that an entirely new leaf 
is formed. Dr. J.S. Newberry® states that he has observed the two species run- 
ning together, and that in certain intermediate regions he has seen trees 
upon which both single and double leaves were fou nd. This would surely i in- 
dicate a very close Joeomeneetia er ” im their minute structure, but in oS 
absence of specimens from l d judgme 
Dr. Hooker® still claims, from his own nckagty that they a are distinct. 1 
Dr. Newberry’s testimony is confirmed by a study of the minute structure of 
these intermediate forms the question would seem to be settled. 
9. P. edulis Engelm. Closely resembling the last, but the 
much smaller section sas | aed le pate or rarely triangular 
(3-leaved): stomata in 5-15 ro ducts .030-.060 mm. : num- 
ber of cells in bundle-sheath 1 15-40: leaves somewhat shorter. 
S. Colorado, New Mexico, and W. Texas. 
The 3-leaved forms of P. edulis we have received raise the question whether 
they should not rather be referred to the next species, not so much on account 
of the 3-leaved character, but because it is accompanied by the absence of dor- 
sal stomata. 
+ +  Nostomata on dorsal side of leaf. 
++ Dorsal side of leaf much broader than either ventral: cuticle nct spe- 
cially thickened: stomata not deeply set, the subsidiary cells even forming 
slight protuberances. 
10. P. ecembroides Zucc. No ventral furrows: stomata 
4-6 rows: dorsal ducts two, nearer the edge than the middle 
(.025-.040 mm.), completely surrounded by strengthening cells, 
which are also in fibro-vascular region : leaves (3) slender, 1-2 
in. lon 
Piroaghont the southwestern mountains and Mexico. 
Occasional specimens of this species show stomata on dorsal side of leaf 
and ey a close relationship to the preceding group. 
P. latisqaama Engelm. Like the last, but with a broad 
fiver on each ventral fie’ ducts smaller (.020- 0-.030 mm.), not 
‘always completely surrounded by strengthening cells : leaves 
more slender and longer. 
exico. 
Resembling P. cembroides, but 
P. Parryana Engelm. 
wih ole much (often twice) larger: stomata in 8-10 rows: 
— verre Pee Club, xii. 50; xiii. 183. 
*s Chronicle, July 31, 1886. 
