Structure of the Leaves of Catamites. 185 



meter ( T 2 -g- of an inch) from side to side, and -^ of a millimeter 

 (g~ of an inch) from the middle of the upper surface to that 

 of the lower. If we may combine these dimensions with 

 those of the leaf shown in Fig. 3, we shall get a leaf 

 measuring upwards of 2 J millimeters ( T V inch) in length, 

 f millimeter ( T 2 g- inch) in breadth, and -£2 millimeter (J^ inch) 

 in thickness. As a very moderate sized Chara leaf would 

 exceed this, at least in length, it is obvious that the Cala- 

 mitean leaves here dealt with are extremely small, a point 

 to which I shall return. 



5. The specimen last described is so well preserved and 

 complete that I have taken it as a standard of reference 

 with which others might be compared, in order to see 

 whether the form and structure described were at all modi- 

 fied, either in different leaves or in different parts of the 

 same leaf. A large number of such comparisons have been 

 made, with the result of showing that in both respects 

 modifications are not uncommon. 



Fig. 5 shows one of the more extreme modifications met 

 with in the form of the transverse section. It is taken 

 from a preparation in the Cash Collection by Mr. Binns, 

 and represents a leaf section whose lower half has a 

 triangular form while the upper half carries a strong 

 median elevation, flanked by a smaller one on each side. 

 The assimilating tissue has been destroyed, but it seems to 

 have been developed on all sides, and the " melasmatic " 

 tissue forms a complete ring. The tissue of the central 

 cylinder has not been preserved. 



In Fig. 6, from the same preparation, we have a leaf 

 section with a single median and two marginal ridges 

 projecting from the upper surface, while the lower half of 

 the section has a rounded rather than a triangular outline. 

 The assimilating tissue and the " melasmatic " are again 

 continuous. Within the central cylinder is the delicate 

 vascular bundle, . which presents itself in an extremely 



