437 



ening tissue occurs close to the bundles; it is almost entirely 

 absent from certain species and is fairly well developed in 

 others; it consists of two parts — the fibrous tissue outside 

 the leptome, and a band of lignified parenchyma uniting the 

 bundles. Both in the stem and in the rhizome of B. acer a 

 smaller amount of stereom occurred in the specimens from 

 the northern localities than in those from Denmark. The nodes 

 in the species of Ranunculus with creeping stems resembled 

 in structure the rhizomes in the species with Ртиг</а- structure. 



In several cases the monostelic structure mentioned by 

 Marié could be demonstrated in the peduncle while the rest 

 of the stem was more or less distinctly schizostelous. 



The pith was often found broken down. 



The cortex was very loose in structure in the majority of 

 the species (cf. for instance R. glacialis and Pallasii) and very 

 often great parts of it were broken down. Anemone Richardsoni 

 and especially Coptis trifolia and Thalictnmi alpinum had a 

 firmer cortex than had the other species, and the epidermis 

 in the last two had also a more xerophytic character ; in the 

 species of Ranunculus it was rather thin-walled ; the cuticle 

 was usually found to be thin and striped. The epidermis con- 

 tained chlorophyll in all the species, often in great quantities ; 

 the stomata were either on a level with the surface or pro- 

 jected slightly. 



Vll[. The structure of t^he leaves. The species which 

 have been investigated may be referred to two large groups, 

 viz., the submerged-leaved and the aerial-leaved. 



A. The typical submerged leaves in Batrachium con- 

 fervoides and R. reptans are cylindrical and more or less radial; 

 Batrachium has one bundle in each lobe, R. reptans has no 

 doubt usually three in each leaf. When these plants grow in 

 dry localities the leaves of both species react in a similar 

 manner and approach the bifacial type to which the elliptical 

 leaves of R. reptans may be referred entirely. The submerged 



