306 Schively — Contributions to the Life History of 



If a transverse section is taken from the stem of a plant 

 about fifteen inches high, there will be seen a single row of 

 cells in the inner cortex, in which may be distinguished 

 small crystals. Just how soon after germination this forma- 

 tion begins has not been definitely ascertained, but evi- 

 dently it occurs quite early in the plant's career. The in- 

 crease in size and number of crystals in these cells is rapid. 

 Finally a distinct crystal sheath (Plate XXIV., Fig. 4,) sur- 

 rounds the vascular area. It is considered that this crystal 

 sheath is equivalent to the original bundle sheath; the 

 position occupied by the former seems to correspond ex- 

 actly to that of the latter. These crystals seem to be 

 surrounded by a protoplasmic film of considerable thick- 

 ness, as this area stains very deeply. This condition is 

 plainly shown in a section taken from a plant stem three 

 months old (Fig. 2). In Fig. 3, is seen a transverse 

 section of a stem, a little older than the preceding, 

 but which, having grown during the summer, was much 

 more vigorous. There is a marked increase in the 

 xylem and also in the phloem. The hard bast appears to 

 have undergone some transformation, very few of the cells 

 are visible and these are in scattered groups. The crystal 

 cells referred to above have greatly increased in number, 

 and are abundantly present in the outer expanded ends of 

 the medullary rays. As yet no reagent that will dissolve 

 the crystals has been found ; but it is possible that treat- 

 ment by several chemicals in succession will accomplish it. 



A transverse section of stem of a plant raised from an aerial 

 seed shows, when three months old, a condition similar to 

 that seen in Plate XXIV., Fig. 2 ; but the diameter of the 

 section is about % of that represented in Fig. 2. 



Yet one more feature of interest is found in the section 

 Fig. 3, when studied with high power. In the xylem and 

 to some extent in the phloem, are noticed sack-like bodies 

 whose contents are refractive, and gelatinous in appearance 

 — some protoplasmic substance possibly : Chlor-iodide of 

 zinc colors these a deep purple-red : iodine test gives no 



