174 JIE.MOIES FKOM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 



species are not situated radially to the centre of the collateral bundles, as is usually the 

 case, but they are quite a distance oS to one side, this deviation being due apparently to 

 the tortion of the twining stem. The xylem is more or less extensive but weak, large 

 portions of it appearing more like wood-parenchyma than like true woody fibres. The 

 fibres are large, 10-20 fi in diameter and 200-250 ^ in length ; the septa are either trans- 

 verse or oblique, and we find no real tapering ends; in cross section they appear square 

 or oblong, with the long axes radial. The larger tracheae are not plentiful, and most of 

 them exist in the ends of the bundles which penetrate the pith as long sharp wedges. 

 However, we find all the varieties represented ; furthest out are the spiral vessels, near 

 these occur border-pitted vessels of about the same calibre ; in the midst of the wood- 

 })arenchyma are small tracheides more or less strongly marked with border-pits, and we 

 find large scalariform tracheides which may merge into those marked with border-pits. 

 AVeak annular vessels exist near the pith, and their markings are often very faint. The 

 diameter of the tracheides and vessels varies from 20-50 n in extreme cases. 



After passing a row of large (110 // X 70-120 ^) parenchymatous cells, the pith con- 

 sists of cylmdric or prismatic cells which measure as high as 100 ,« in diameter and vary 

 from 250-350 ^ in height. 



SUBGENUS ECHINOCAULON. 



Polygonum arifolium. Plants with Aveak stems and a reclining habit constitute 

 this subgenus. They usually grow in damp or wet places and climb over surrounding 

 objects by means of recurved prickles. We find here quite a characteristic anatomical 

 structure. The epidermis is double, averaging about 50 fi. The periblematic cylinder 

 is not well developed and measures from 50-70 [z. The plerome derivatives are strong, 

 ranging, with the exception of the pith, from 200-350 f^, and each part is well developed. 



This is the only instance where I have found a double epidermis ; the inner layer 

 of cells is somewhat larger than the outer, the difference often amounting to 10 ^u; their 

 diameter ranges from 10-30 ^ and their length from 40-80 [i. Four kinds of trichomes 

 spring fi-om the epidermis: First, we have simple multicellular hairs with long sharp 

 points ; second, somewhat stouter hairs which fork into from two to six prongs ; third, 

 long glandular trichomes bearing yellow or black glands at the apices, and finally 

 prickles, which are more or less recurved. 



The primary cortex is rather meagre, but in some long sections prominent. The 

 cells are long prisms of various shapes and sizes ; their diameter ranges from 10-70 [i, and 

 their length from 30-150 fi. The elements of the starch-ring do not differ much from 

 those of the hypoderma ; they have, on the whole, a greater diameter and vary from 



