Manchester Memoirs, Vol. lix. (1915), No. 3. 3 



Isoetes I am in agreement and do not propose to discuss 

 the phylogenetic question further here. 



While certain detailed resemblances (especially in the 

 root, leaf-base, ligule and sporangium) justify the inference 

 of relationship between Isoetes and the Lepidophytinae, 

 larger morphological questions remain, and are only made 

 more interesting by the suggested phylogeny. How are 

 we to compare the total organisation of an Isoetes plant 

 with that of lepidodendron or Sigillaria ? What are we 

 to understand in detail by Isoetes representing the last 

 stage of reduction of the Lepidodendron type ? Can we 

 trace a distinction of a leaf-bearing shoot and a root- 

 bearing basal region in Isoetes corresponding to the striking 

 distinction of these regions in the Lepidodendreae ! Such 

 questions invite detailed and critical consideration of the 

 morphology of the stock of Isoetes as expressed in its 

 adult structure, its continued growth and its ontogeny. 

 In this series of papers it is hoped to make some contri- 

 bution to this necessary preliminary to further comparison 

 between Isoetes and the Lepidophytinae. 



General Morphology of the Stock of 

 Isoetes lacustris. 



This paper will deal with some features of the general 

 organisation and gross anatomy of the stock of Isoetes, 

 leaving details for consideration in subsequent papers. 

 The uniformity of general organisation in the genus 

 Isoetes makes it probable that conclusions derived from 

 the study of one species will hold in the main throughout. 

 The description in this preliminary paper will be limited 

 to the usual two-lobed stocks of our native Jsoetes lacustris, 

 partly because abundant material could be obtained and 

 partly because the various planes of section can be readily 

 defined in the case of the two-lobed stock. 



