8 Lang, Morphology of the Stock of Isoetes lacustris. 



is well known, though many of the published figures are 

 not accurate in detail. 11 It is important to start with a 

 clear idea of the form of the stock and of the nature of 

 the surfaces bounding it, and the accompanying diagram 

 {Fig. i) will assist in this. The mature functional leaves 

 are arranged spirally and stand in a close group around 

 the summit of the stock. They conceal and protect the 

 conical apical depression on the sides of which stand 

 the developing leaves for future seasons. The cortex 

 bearing the functional leaves is still intact but the older 



Fig. I. — Diagram to illustrate the surfaces of a two- 

 lobed stock of Isoetes. 



Description in the Text. 



leaf-bearing cortex is split into the two lobes, the upper 

 surface of which bears the withered bases of the leaves of 

 former seasons. This leaf-bearing surface {Fig. i t a) is 

 clearly part of the true outer surface of the shoot. On 

 the other hand, the splits that divide the leaf-bearing 

 cortex into the two lobes expose surfaces (Fig. I, If) that 

 cannot be regarded as parts of the true outer surface of 

 the plant. These splits in the leaf-bearing cortex are the 

 continuation upwards of the groove or split across the 



1 ' The figures reproduced in Seward's " Fossil Plants " (Vol. II., 

 I'ig. 132) show the position of the roots and root-scars accurately. 



