i 9 o8] THIESSEN—DIOON EDULE 359 



given by Mettenius. It was the first correct statement of the facts, 

 but their meaning was probably not understood until an interpreta- 

 tion of the situation was given in 1886 by Bertrand and Renault (5). 



The second paper upon the vascular anatomy of Dioon is that of 

 Matte (6), a brief description of the anatomy of two seedlings being 

 given. In one of them, a very young seedling, the cotyledons were 

 unequal,' the larger having four vascular bundles, and the smaller 

 having two small bundles, but with two other very small strands at the 

 very base, one on each side of the other bundles. The bundles con- 

 tinue in a vertically descending course until where the foliar bundles, 

 after being arranged in a circle, have been reduced to four large 

 bundles, separated by medullary rays. The six cotyledonary strands 

 turn now abruptly toward the three poles (protoxylem groups) of 

 the root, converge, and unite two by two in front of them, effecting 

 an entrance through the medullary rays separating the foliar bundles, 

 and unite their phloem with the phloem of the stem. Their second- 

 ary xylem unites laterally with that of the stem, while the primary 

 xylem seems to be in direct continuity with the tracheal poles (pro- 

 toxylem groups) of the root. The centripetal xylem disappears in 

 the passage across the medullary rays. 



In the description of the older seedling Matte found in each 

 cotyledon four bundles of equal size. Their course and method of 

 union is comparable with that found in the other seedling, and they 

 still unite two by two in converging toward the poles (protoxylem 

 groups) , but these poles are four in number. 



Matte touches also upon the girdling habit, ascribing it to an 

 intercalary growth produced under the influence of the development 

 of new interior leaves. The vascular strands of the youngest leaves 

 pursue a vertical course, but those of the older ones an oblique 

 course, a comparison of leaves of different ages showing that this 

 departure from a direct course is due to intercalary growth. 



Methods 



Embryos were removed from mature seeds and killed in chromo- 

 acetic acid, imbedded in paraffin according to the usual methods, 

 cut with a rotary Minot microtome, and mounted in series, much care 

 being taken that no sections were lost or misplaced. When only the 



