SCIENCE-GOSSIP. 



373 



forests plant life seems in a manner to lose com- 

 mand over itself and exhibii phenomena with 

 which we in temperate climes arc unacquainted. 



For instance, notice the central port ion. The 

 wood at fir.-t is developed with great regularity 

 and strongly lignified. Then on the entire peri- 

 phery a great change becomes visible, a more open 

 formation taking the place of the previously 

 regular tissue. Zones of thick and thin, lignified 

 and unlignified tissues alternate, which in a tem- 

 perate clime would be taken to denote successive 

 periods of growth and rest. Beyond this we come 

 to a zone of cambium, or wood-producing tissue, 

 on the outside of which is the soft bast or phloem, 

 and then wood again, and this order continues till 

 we come to the bark. In the plants with which we 

 are familiar the wood cambium is invariably found 

 occupying one definite position, and I think few are 

 familiar with any plants which have more than one 

 legular. system of wood cambium. Fascicular 

 cambium and cork cambium do not here concern 

 us. This cambium is derived from the thin-walled 

 cells of the ground tissue, and under great stimula- 

 tion it is conceivable that any portion of thin- 

 walled elementary tissue with active contents might 

 develop a cambium. Now as regards the object 

 before us, my views are that the outermost cells 

 of the primary soft phloem or else the inner cells 

 of the cortex developed a second cambium which 

 proceeded to form new wood and phloem tissue, 

 and to develop on exactly the same lines and at 

 the same time as the original cambium. So that 

 now we have two sets of wood-forming cambium 

 simultaneously at work. When this new growth 

 had developed the same thing occurred again until 

 the present state of development had been arrived 

 at. As the greatest increase in thickness has 

 always taken place in one direction, it naturally 

 follows that the cortex and sclerenchyma will be 

 folded back laterally and that we shall always find 

 this hard tissue in its usual place, i.e. at the 

 periphery. In this section we see four bands of 



Pig. 1. Transverse Section of Stem oi Brazilian Lianas. 



cambium and four bands of wood and four bands 

 of phloem-tissue on either side of the centre, and 

 all appear to have been in an active condition at 

 the time of gathering. The cambium at the outer 

 edge of the latest woody increase is very clear. 

 Of course my theory requires practical proof 

 such as could only be obtained by observa- 

 tion on the living plan! and by tracing its 

 development. These remarks are made about 

 fig. 1, but they apply also to fig. :!. and I do 

 not think it would be very difficult to account 

 for the complicated arrangement shown in this 

 section. Perhaps some of our members will give 

 their views on the subject. The only section 

 which would satisfactorily prove the cohering 

 theory would be one which showed component 

 areas with a totally dissimilar structure. In a 

 case like fig. 3 one could better understand their 

 division into nine separate twigs rather than their 

 cohesion. — T7ios. S. Beardgmore. 



I think if Mr. Beardsmore regards fig. 1 as a 

 series of climbers, the central being the original 

 stem, (In others clinging to it one upon another, 

 ami the section cut through a plane where there 



were three stcm> on either side, the cohesion diffi- 

 culty will disappear. The inner xylem of the 

 younger climbers is not formed owing to lateral 

 pressure due to cohesion, but the xylem has been 

 formed outwardly. We have a familiar example 

 of younger climbers from the same shrub surround- 

 ing and clinging to the older stems in the honey- 

 suckle. Fig. '■'> is another example of tropical 

 climbers, some of which produce trunks resembling 

 cables.—/ 1 '. ('. Fuller. 



-\k*2' 



Fig. 2. Transverse Section of stem of Brazilian Lianas. 



The type of fig. 1 is figured and described in 

 Kerner & Oliver's " Natural History of Plants," and 

 the explanation there given agrees with 3Ir. 

 Beardsmore's theory. We may therefore accept 

 it without hesitation as the true one. A structure 

 somewhat analogous is found in the Cycads, but 

 here there are several complete rings of cambium, 

 each ring forming xylem internally and phloem 

 externally. In fig. 2 certain parts of the cambium 

 ring appear to give up the formation of xylem and 

 devote themselves entirely to the manufacture of 

 phloem. This seems to take place in a remarkably 

 orderly manner, the demand for an increased supply 

 of phloem being made by the plant at fairly definite 

 intervals. This arrangement seems capable of an 

 interesting physiological explanation, which may be 

 something like the following : The humid atmo- 

 sphere of a Brazilian forest would perhaps tend to 

 check rapid transpiration, while the absorbed liquid 

 being fairly rich in inorganic food materials a very 

 active transpiration current would not be necessary. 

 Consequently xylem. which is the essentially water- 

 conducting tissue of the plant, would not need to 

 be so extensively developed as in a plant growing 

 under other conditions. Bui assimilation is rapid. 

 and large quantities of organic material are manu- 

 factured. This needs phloem for its conduction 

 from place to place. Hence the somewhat ab- 

 normal development of this tissue in the stem. 

 Another interesting point about this slide is the 

 presence of tiillen or tyloses in the vessels. In 

 this connection the following paragraph, taken 

 from Vine's "Text-book of Botany." may be of 

 interest : " When a tracheal cell with a fitted 

 wall abuts upon cells containing living protopL - 

 it not infrequently happens that the thin jut- 

 membranes begin to bulge, in consequence of the 

 pressure upon them of the contents of the living 

 cells, into the cavity of the tracheal cell, and 

 actually grow. Cell division may take place in 



