574 



SCIENCE- G OSSIP. 



these ingrowths, so that a mass of cellular tissue is 

 found in the cavity of the tracheal cell. These 

 ingrowths are termed tyloses ; they are constantly 

 to be found in some kinds of wood — e.g. Kobinia — 

 occasionally in many others." With regard to 

 fig. 3, though I am unwilling to admit the cohesion 

 theory, it is hard to suggest any other explanation. 

 If the case were really one of cohesion, would there 

 not be some line of demarcation between the re- 

 spective stems 1 In fig. 4 the regular groups of 

 lignifiecl cells towards the periphery seem to be 

 strands of sclerenchyma developed in the phloem. 



Pig. 3. Transverse Section of Stem of Brazilian Lianas. 



That it is not of the same nature as the true xylem 

 towards the centre is indicated by the fact that the 

 peripheral lignifiecl tissue contains no vessels. If 

 this view be taken the structure of this stem is 

 comparatively normal. — C. J. Wilkinson. 



Mr. Beardsmore states that he can find no 

 information in botanical works concerning Lianas, 

 or, as I have generally seen it spelt, Lianes. I find 

 on referring to Henfrey's " Botany " and Balfour's 

 " Class-book of Botany " that both contain informa- 

 tion on the subject, although perhaps not all the 

 information one might wish. Henfrey, on p. 233, 

 and Balfour, on p. 85, give an illustration of the 

 stem in fig. 1. The former describes it as a 

 peculiar fasciculated stem of a Malpighiaceous 

 plant of South America. The stem presents an 

 example of an anomalous exogen. It consists of 

 numerous woody masses, having each distinct pith, 

 and surrounded by cellular tissue resembling that 

 of the outer bark. Such a stem, he says, looks as 

 if it were formed of several united together. He 

 offers no explanation of how this is produced, but 

 refers one for an account of anomalous exogens to 

 the works of De Jussieu and others. The only 

 book that I have at hand that offers any explana- 

 tion of how these appearances may be produced is 

 Goebel's " Classification and Special Morphology 

 of Plants," and the information appears to be taken 

 for the most part from De Bary. A few short 

 extracts may be interesting. In describing the 

 histology of the stem in dicotyledons he says : 

 "Very striking deviations from normal structure 

 are to be found in the Sapindaceae. Some species 

 of the order are formed in the usual manner, 

 but in others the transverse section of the stems 

 shows, in addition to the usual ring of wood, a 

 number of smaller closed rings of different sizes in 

 the secondary phloem, each of which increases in 

 thickness, like the ordinary ring, by means of a 

 layer of cambium " (fig. 3). Nageli supposes the 

 principal cause of this to be that the primary vas- 

 cular bundles of the stem do not lie in a circle or 

 transverse section, but in groups more towards the 



outside or inside. When the interfascicular cam- 

 bium is formed in the fundamental tissue the 

 isolated bundles are connected together, according 

 to- their grouping on the transverse section, into 

 one closed ring in Paullinia, or into several in 

 Serjana (Se?jana, Balfour, p. 780). Goebel groups 

 these abnormal arrangements under several 

 headings : under C, " renewed thickening rings," 

 there are some remarks that apply to fig. 1. 

 Growth in thickness begins in the normal manner 

 and then ceases, but is afterwards continued by a 

 new cambium zone formed in the parenchyma, out- 

 side the first one. The process may be repeated 

 and a number of concentric zones be formed. This 

 mode of proceeding, which has already been 

 described in Cycas and Gnetum among the 

 Gynosperms, is found in Dicotyledons in the 

 Menispermaceae, and in the stem of Avicennia. 

 In the latter cases all the zones of increase which 

 succeed to the normal one are formed in the 

 secondary phloem. In the stem of some lianes 

 (BauJiinia), , in Wisteria and others the new 

 zones are formed in the secondary phloem 

 (not in the primary phloem, as Mr. Beardsmore 

 suggests). Beferring to the mode previously 

 described under Cycas and Gnetum, I find 

 (p. 344): "In Gnetum, as in the Cycadeae and 

 many Dicotyledons, the growth in thickness from 

 the first cambium ring ceases after a time, and a 

 new zone of meristem (i.e. actively dividing 

 tissue) is found in the secondary cortex out- 

 side the ring. In this zone xylem-strands are 

 formed on the inside and phloem-strands on the 

 outside, alternating with medullary rays. As this 

 process is repeated more than once, a transverse 

 section of an older stem or branch of Gnetum 

 scandens, for example, shows several concentric 

 rings of growth, each consisting of a xylem-ring 

 and a phloem-ring." In fig. 1 these zones are 

 found laterally and not concentrically. Mr. 

 Wilkinson's interesting' account of fig. 2 leaves 



Fi&. 4. Transverse Section of Stem of Brazilian Lianas- 



very little to add. There are many other interest- 

 ing points contained in Goebel's book, but I think 

 it unnecessary to quote further, as anyone inter- 

 ested in the subject can read the entire account 

 for himself. Nothing is said, however, about 

 cohesion. As Mr. Beardsmore says, it needs no 

 elaborate botanical knowledge to settle this ques- 

 tion. An appeal to common sense decides at once 

 against the cohesion theory. I have endeavoured 

 to record the unusual appearances which these 

 slides present by photographs. The task has been 

 rather a difficult one for me, as I have never before 

 photographed with such very low powers, and I 

 found some trouble in getting an even illumination 

 of the object and in judging the length of time 

 necessary for exposure. — J. It. L. Dixon. 



