42 DOUGLAS HOUGHTON CAMPBELL ON THE 



are remote from each other, being separated by about one-third of the circumference of 

 the stem, but owing to the fact that the stem is somcAvhat twisted, it is not easy to deter- 

 mine whetlier or not the fourtli leaf stands directly above the first. "Wlien quite small, 

 the stolons are crowded between the base of the leaf and the rhizome, so that they are 

 flattened, and the angle of divergence of the earliest leaves appears to be one-half. 

 The sui-face, both of the stem and scale-leaves, is smooth and of a dark, reddish brown 

 color. At the tip, the younger parts are greenish, chlorophyll ajDpai'ently being formed, 

 even Avhen the stolon is completely iinderground, and of course shut off from the influ- 

 ence of light. 



The stolon, Avhen first formed, is very slender, but a short distance above its insertion 

 it suddenly enlarges, so that it assumes a club-shape. Up to this point no leaves have 

 been developed, and a section through the enlarged apex shows that this enlargement is 

 due in part to the formation of the first leaves. The apex is nearly flat and much broad- 

 ened on account of the inci'eased lateral growth. It consists of a mass of small cells 

 developed (i-om the apical cell, and these soon become separated into plerome and peri- 

 blem, the dcrmatogen not being readily made out in the xcry 3'oung stolon. The plerome 

 in the basal parts is a simple cylinder of uniform size, but just below the first leaves, it 

 widens suddenly, and divides later into two masses of procambium cells, separated by a 

 mass of shorter ones. This division of the plerome cylinder takes place about the time 

 that the first tracheary tissue is formed in the lower part of the stolon. . As the perma- 

 nent tissues develop in the bundle, this central mass of short cells forms the medullary 

 parenchyma which comnnmicates with the cortical parenchyma, b}^ the foliar ga])s, as in 

 the main rhizome. The separation of the medullary parenchyma from the pi'ocambium 

 begins before the bundle divides, thus occupying the center of the perfectly cylindrical 

 bundle, and sin-rounded by an uninterrupted mass of procambium, which ultimately forms 

 the hollow axial biuidle that traverses the stolon for a short distance from its base. 



The apex of the older stolons is more conical, and the apical cell has the form of that 

 of the mature stem : — a tetrahedron with nearly equal latei'al faces from which segments 

 are cut off in the same way. The mass of meristem cells developed from them can soon 

 be separated, as in the younger stolon, into plerome andperiblem, the former soon shoAv- 

 ing the central shorter cells and the outer elongated procambimn cells, the procambium 

 cylinder being interru2)ted by masses of shorter cells like those of the medulla, and con- 

 necting the latter with the cell of the periblem. These spaces, the foliar gaps, become 

 later much elongated on account of the great length of the internodes, but there are biit 

 three of them in a single cycle, corresponding to the primitive one-third arrangement of 

 the leaves like that of the yoiuig germ plant, each leaf probably representing a segment 

 of the apical cell. 



The first tissue to assiuiie the permanent foi'm is the cortical parenchyma Avhich in the 

 slow-groAving younger stolons can be traced up nearly to the apex. The cells are ii-reg- 

 ularly polyhedral in form, and distinct pits are early developed upon their walls. They 

 contain small starch grains in considerable quantities, but no other conspicuous contents. 

 !N^o definite h^qjoderm is formed in the young stolons, l)ut one or two layers of the outer 

 cells acquire, veiy early, dark brown Avails. The ground tissue is almost complete and its 

 cells full groAvn, before any permanent tissue is dcA'eloped in the fibro-vascular bundle. 

 The procambium cells are long and narroAv A\'ith oblique ends, and filled Avith granular. 



