268 Mr G. F. Scott Elliot on the 



an axis of inflorescence or flower stem, accompanied with a 

 vegetative branch of the same thickness in the same plant, 

 may also be noted, and some direct experiments have also 

 been attempted. 



The contents of laticiferous vessels are not fully known ; 

 but, on the one hand, they contain ferments dissolving 

 albumen as well as albuminoids, also sugars and gums, 

 alkaloids, &c., and, on the other hand, products which may 

 be regarded as effete. From their intimate connection 

 with the conducting tissues and from the w^ay in which 

 they appear to replace the spongy parenchyma and 

 parenchymatous sheaths, he infers that they act chiefly as 

 conducting organs for plastic building materals. Schullerus 

 points out also that the richness of the laticiferous vessels 

 in these substances (plastic building material) is greatest 

 during the active development of the embryo and germina- 

 tion of the seed, and is least in the period of quiescence. 

 Their contents are also thin and watery in etiolated plants. 

 At the same time, however, they do contain useless and 

 effete products. 



As regards the different types of vascular bundles, he 

 regards the concentric as the primary, while the radial 

 arrangement of the root is a modification to connect the 

 absorbing root epithelium directly with the vessels, and the 

 arrangement of the leaf bundle similarly connects them 

 with the assimilating tissues. 



{d) Reservation Tissues (Store System). — If a section be 

 made of the endosperm of a seed, a series of curved lines can 

 be seen radiating from the embryo to the surface. The elon- 

 gated reserve cells of the endosperm He along thesecurves,and 

 thus they may act as mechanical supports, while at the same 

 time they afford a constant supply of material to the embryo. 



{e) Aeration System. — The intercellular space increases the 

 surface in the plant which is exposed to air. They are thus 

 specially adapted to transpiration of water vapour, &c., and 

 accordingly show great modifications according to climate 

 and habitat. 



For example, the two layers of palisade cells (the cells 

 being rounded) form two systems of intercellular spaces at 

 the corners. In Hahea suaveolens these are not in free 

 communication at all points. The intercellular spaces in 



