56 BuHling — Tlic Structure of the Cork Tissues in 



older layers at the outer margin of a section, as in different 

 species of Poteiitilla and in Fragaria indica. This arrangement 

 is shown for Potcntilla noii'cgica in Plate X, Fig. i. In 

 Fragaria indica, Potentilla chrysantlia, P. geoidcs and P. alpes- 

 tris, the alternation of pigmented uniseriate and unpigmented 

 multiseriate layers is not so marked a feature, especially if 

 material is obtained during the late autumn, winter or early 

 spring months. After treatment with iodine and sulphuric 

 acid, however, the annular condition is very clearly defined. 

 This may also be the case with some species of Gcian. In 

 Geuni atrosanguincuvi (Plate X, Fig. 2), quadrangular in- 

 tercellular spaces are present. The alternation as to the 

 size of the cells in the uniseriate layers is not so clearly shown 

 in this species as in G. allntin, G. la'banuni and G. rivale, but 

 proof that the cell walls in the alternating layer are suberized, 

 is obtained by the use of sulphuric acid and iodine. 



Group Agrinionica;. — The following five species have been 

 examined : Agrimo7iia Eupatoria, A. parvifiora, Alcheniilla pyre- 

 naica, A. pubescens, Poterium Sangidsorba and AccBna reptans. 

 Intercellular spaces are present in the cork region ; and, as in 

 some species of the last group, the cork is arranged in flattened 

 compact uniseriate layers alternating with multiseriate layers 

 of less compact cells. This condition is illustrated in Agii- 

 monia Eupatoria (Plate X, Fig. 3) ; Agrimonia paiinfiora 

 (Fig. 4), and in Alchemilla pyrciiaica (Fig. 5). As regards inter- 

 cellular spaces, the most remarkable arrangement is found 

 in Agiimonia parvifiora. The cork region of this species 

 may be described as follows. Immediately external to the 

 cork cambium is a single layer of compact flattened cells 

 with brown pigmented cell walls, while a brown pigment 

 fills the cell cavities ; outside of this are three layers, the cells 

 of which are so arranged as to form radiating beaded spokes. 

 The inner two, of each triplet of cells in this zone, is of medium 

 size, the external one is large, while between the radiating cell 

 triplets are large intercellular spaces. The walls of each 



