oe a, ae ee? A oe OP ae POR NO BER AOS 
LEITNERIA FLORIDANA. 85 
surface. The mesophyll is composed of two or, mostly, 
three layers of compactly placed palisade cells only a little 
longer than broad, occupying the upper half of the leaf, 
and a spongy parenchyma with ample intercellular spaces 
below. No spicular cells have been observed. 
The structure of the roots is interesting to this extent, 
that (at least in lateral roots, which, alone, have been 
examined) they are entirely destitute of secretion passages, 
which are thus seen to be confined to the pith sheath of the 
stem, the intra-fascicular parenchyma of the petiole, and 
the parenchyma of the veins of foliar organs, including the 
carpels. The elements of the root are essentially similar 
to those of the stem, and secondary growth in thickness is 
effected in the manner usual in the roots of Dicotyledons. 
While I have found comparatively little starch in the 
stem of specimens gathered either in November or in the 
spring, the medullary rays and cortical parenchyma of the 
root contain an abundance of roundish grains, often binary, 
and of extremely variable size. 
Dr. Chapman, who described the genus Lettneria and its 
single species, placed it among the Myricaceae because of its 
simple flowers arranged in spike-like catkins;* and in this 
he was followed by DeCandolle.t Subsequently Baillon 
examined it, and placed it with doubt in his group of Cas- 
taneae, beside Myrica, making it, however, the representa- 
tive of a series which he named Leitnerieae,t and in which 
he also placed with question a Madagascar genus, Didymeles. 
This series was raised by Bentham and Hooker § to ordinal 
rank, under the name given by Baillon, and placed between 
the Platanaceae and Juglandaceae, with an indication of 
Urticaceous affinities, Didymeles being excluded. The 
order is maintained under the name Leitneriaceae by 
Engler, || who places it between Myricaceae and Salicaceae. 
~ * Flora So. U. 8. 427. 
+ Prodromus, xvi. (2), 154. 
¢ Hist. des Plantes, vi. 239, 258; Tison, in Baillon, Dict. de Bot. iii. 215. 
§ Genera Plant. iii. 397. 
| Engler and Prantl, Pflanzenfamilien, iii. (1), 28. 
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