220 



plant, being in this instance especially allied to the leaf of a plant 

 belonging to the order Myrtaceee, on account of the presence of a 

 distinct marginal vein. A strong midrib proceeds from the pe- 

 tiole for some distance up the leaf, and is gradually attenuated and 

 expended by giving off numerous branches, which take a curved di- 

 rection outwards and forwards, and which are intercepted before they 

 reach the margin, by the vein running parallel to the circumference, 

 which has its commencement at the petiole and its termination in the 

 apex ; consequently each vein has a tendency to carry its fluid to- 

 wards the apex by the intervention of this marginal vein. And there 

 is no doubt that the fluid is conducted by these courses, for if any one 

 be wounded by a sharp instrument, dropping will proceed from the 

 wound as well as from the point ; besides, the veins do not form pro- 

 minent opaque ribs as in many exogens, but are level with the surfa- 

 ces of the leaf; and when examined by transmitted light they appear 

 the most transparent portions, an indication of their being full of fluid. 



If the attenuated apex of the leaf be examined by dissection, mi- 

 croscopically, it will be found to present some few stomata on its 

 cuticle and a dense bundle of vessels in its centre, surrounded by 

 cellular tissue containing multitudes of acicular raphides; and I could 

 never carry the dissection fine enough to discover whether or not 

 these vessels communicate with the surface or the caverns with which 

 the stomata are connected. 



From the anatomy of the leaf it would appear that the surcharged 

 vessels all propel their contents towards its point, and the excess 

 finds the means of escape as through a filter.* It cannot be from 

 gravity, for it occurs whilst the young leaf is making its appearance, 

 before it unrols, when the sharp-pointed apex is in the most elevated 

 position, being quite perpendicular. If it occurred only when the 

 leaf was pendulous, it might be imagined that the liquid was conden- 

 sed in the cavernous tissue of the leaf, and escaped through the sto- 

 mata fi'om gravity ; but as this is not the case, it must be considered 

 that this peculiarly constructed apex is a beautiful provision — a kind 

 of natural safety-valve, for permitting the superabundance of watery 

 fluid to be readily removed, the retention of which might be connected 

 with unhealthy action in the economy of this elegant plant. 



The escape of fluid from the apex of the leaf is not peculiar to Ri- 

 chardia, as many other plants, when grown under glass will exhibit 



* The apex of the spathe, in its eavly state, will also exhibit the phenomeaon ; as 

 will also a leaf when a fifth of its point has lost the signs of vitality. 



