Manchester Memoirs, Vol. lix. (1915), No. 8. 



VIII. Studies in the Morphology of Isoetes. II. The 

 Analysis of the Stele of the Shoot of Isoetes lacustris 

 in the light of Mature Structure and Apical 

 Development. 



By William H. Lang, M.B., D.Sc, F.R.S., 



Barker Professor of Cryptogamic Bolany in the University of Manchester. 

 {Read January 1 2th, igi$. Received 'for publication Jamtary igtli, iQr$.) 



In the first of these studies the general construction 

 of the stock of Isoetes was considered and the distinction 

 drawn between the shoot and a lower root-bearing region 

 or rhizophore. A corresponding distinction into two 

 regions was seen in the central vascular system of the 

 plant. In this paper some features of the shoot will be 

 considered in detail. The structure of the short stem 

 bearing the crowded leaves is complicated by the slight 

 longitudinal growth and the continued expansion of the 

 cortex. This cortical expansion will not be dealt with at 

 present, so that the chief questions to be considered are 

 the method of apical growth, the differentiation of the 

 stele from the procambium, the primary structure of the 

 stele including the relation to it of the leaf-traces, and 

 the anomalous secondary growth. The analysis of the 

 stelar structure of Isoetes in the light of its apical develop- 

 ment may, it is hoped, contribute to stelar morphology 

 and also afford a better basis for comparison with the 

 stele of the Lepidodendreaj. These general questions 

 will, however, only be touched on in this paper, which will 

 be limited to the description and analysis of the stele of 

 well grown plants of Isoetes lacustris. The description 



May 31st, iy 1 5. 



