Branner.] 460 {April 18, 
moelle des Dattiers est placées dans l’interval des fibres qui vont toujours 
en se serrant du centre & la circonférence, en sens contraire des autres 
arbres, et elles ne sont pas placées par couches comme j’ai en mille fois 
Voccasion de l’observer sur des troncs coupées.”’ 
Although Desfontaines kept comparatively quiet upon the subject, 
pupils of his, and especially Daubenton, took up his theory, and did all in 
their power to give it general acceptance in the scientific world. We know 
how successful they were, for, in 1819, de Candolle published the classifica- 
tion in which all phenogamous plants were divided into endogens and ex- 
ogens. This classification was based upon the theory of Desfontaines, and, 
after its publication, was accepted without question of importance up to 
1824, when Hugo,von Mohl published his ‘‘De Structura Palmarum.’’ 
Previous to Von Mohl, however, Moldenhawer had denied the theory of 
Desfontaines. As stated by Mirbel,* this theory of Moldenhawer was, that 
the fibro vascular bundles in monocotyledons take the place of the woody 
layer in dicotyledons, and that the lignification begins at the centre, and 
gradually approaches the circumference. If Mirbel’s be a true statement 
of Moldenhawer’s theory, I see no reason for considering it of much im- 
portance, as it was only proposing to replace one error by another, 
The next work upon palm structure is that of Hugo von Mohl, published 
in 1824, as an introduction to Dr, OC. F. P. von Martius’ “ Genera et Spe- 
cies Palmarum.’’+ Von Mohl’s work was done so carefully and conscien- 
tiously that although his theories have been attacked, and more or less 
modified by Meneghini and Mirbel, they have been generally and justly 
accepted as the best, if not the true ones, up to the present time. And, 
however much one may disagree with Yon Mohl’s conclusions, he cannot 
help feeling that his work would have been more thorough and more sat- 
isfactory if he had had more extended opportunities for observation. He 
admits that he had only young specimens, and portions of full-grown 
palms to work upon,} and any one who has tried to investigate this sub- 
ject, can appreciate the difficulty or impossibility of demonstrating any- 
thing satisfactorily in a short section of a mature trunk, and may well 
wonder that Von Mohl came so near the truth with such unsatisfactory 
material from which to gather his facts and draw his conclusions. 
Writers upon pa!m structure are continually referring to the difficulty of 
dissection and investigation, and in the literature of the subject we find 
them admitting their inability to make out certain points$ on account of 
the impossibility of following the bundles, 
Next after Von Mohl came Meneghini in his ‘‘Recherche sulla Strut- 
tura,”’ etc.,|| published in 1836, and followed in 1843 by more recent 
observations, under the title of ‘‘Intorno alla Struttura,’’ etc. || 
*Comptes Rendus de l’Acad. des Sel., 1848, Vol, I., p, 1216, 
+See under Von Moh! in literature at end, 
{V. Ray Society, 1849, pp. 73-77. 
# Ray Society, 1849, p. 85. 
| V. literature at end, under Meneghini, 
