LATICIFEROUS VESSELS OF HEVEA. 5G7 



the radicle having scarcely begun to burst the envelopes of the 

 seed on the 11th day. Iu the oldest the stem has attained a 

 length of about ten inches, and already bears a pair of (opposite) 

 well-developed leaves. 



The investigation of this material has resulted in the complete 

 confirmation of the conclusions arrived at from my previous 

 examination of the older stem of E. Spruceana. The differences 

 chiefly affect details, the most important beiug that the hypo- 

 dermal system of laticiferous vessels described in H. Spruceana 

 is absent in H. brasiliensis, at any rate in the hypocotyledouary 

 stem and the first epicotyledonary internode. Other differences 

 no doubt depend on the different stages of development of the 

 plants investigated. 



In the embryo of H. brasiliensis at the commencement of 

 germination histological diftereutiation has already made con- 

 siderable progress. At this stage the radicle is extremely short, 

 with a very blunt apex, which is surrounded by a whorl of young 

 lateral roots. The hypocotyledouary stem is very short, and 

 there are two large broad cotyledons. During germination the 

 latter remain imbedded in the endosperm. As might be expected, 

 the tissues of the cotyledons are at the beginning of germination 

 more advanced in their development than those of any other 

 organs of the embryo. The network of vascular bundles is well 

 differentiated, many elements of the xylem having the usual 

 spiral thickenings already formed. The laticiferous tubes occur 

 on the phloem side of all the' bundles, and are limited to this 

 position, none of them being present in the parenchyma between 

 the bundles. They are already well developed, and form a com- 

 plex anastomosing system containing abundant latex. Numerous 

 and extensive perforations occur in the lateral walls. The coty- 

 ledons afford the most favourable material for the observation 

 of the mode of development. Though the differentiation of 

 the laticiferous tissue is so far advanced, the absorption of the 

 transverse walls is still by no means complete. In many cases a 

 rim of cellulose remains, marking the position of a wall, the 

 greater part of which has disappeared (fig. 2, f and f). In 

 other cases we find a perforation at one side of the transverse 

 wall, the latter still extending across more than half the diameter 

 of the vessel (figs. 1, 2, f), while in others again the transverse 

 walls, though reduced in thickness, show no obvious perforations. 

 Here, then, we once more have an example of what appears to be 



