GERMINATION AND EMBRYOGENY OF GNETUM GNEMON, 287 



Hitherto we have considered the structure of the seedling 

 before the development of the plumule. In plants in which 

 the first plumular leaves are already formed a system of 

 vascular bundles similar to that of the hypocotyledonary 

 stem is found in the first internode of the plumule ; as they 

 pass downwards the bundles branch, and coalesce laterally 

 at the point of insertion of the cotyledons. Of the result- 

 ing bundles, which are reduced by successive lateral fusions 

 to a small number, some insert themselves upon the bundles 

 of the cotyledonary system, others (usually four) continue, 

 for some time at least, a separate course between the cotyle- 

 donary bundles. 



Meanwhile an interfascicular cambium appears in the 

 hypocotyledonary stem, while the original bundles undergo 

 secondary thickening; the vascular ring is thus completed. 

 It is worthy of observation that there is an irregularity in 

 the development of this ring immediately above the feeder ; 

 here, on the side of the stem opposite that organ, /. e. 

 where there is a direct vascular communication with the 

 root, the xylem is more strongly developed than on the side 

 next the feeder ; the reverse is the case, though in a less 

 marked degree, with the phloem. These observations are of 

 importance when connected with the fact that the seedling 

 is dependent upon the root for its supply of water, and upon 

 the endosperm for its supply of nutritive materials. 



The secondary thickening of the vascular system of the 

 root is derived from two cambium zones, similar in 

 position to those of Welwitschia ; in the oldest roots as yet 

 investigated the activity of this cambium remains, while 

 there is no formation of peripheral bundles as in Wel- 

 witschia. The same is the case with the stem. 



Sclerenchyma. 



In the pith and cortex of the stem are found sclerenchy- 

 matous structures of various sorts: (1) such as are obvi- 

 ously derived from cells of the parenchyma, the form of 

 which they retain ; their walls are pitted and lignified ; 

 (2) cells with the same characters as the above, but with 

 stellate form, each cell having formed one or more conical 

 outgrowths, which follow the intercellular spaces; (3) 

 tOAvards the periphery of the stem (and root) are found long 

 unbranched sclerenchyma fibres with smooth walls ; when 



Micr. Sci.,' Oct., 1881, p. 577) is incorrect. In this plant also both bundle 

 sheath and some cells of the cortex take part in the formation of the 

 lateral roots. 



VOL. XXII. NEW SEE, T 



