702 KEPOET — 1886. 



10. On Heterangmm Tilioides. 

 By Professor W. C. Williamson, LL.D., F.B.S. 



In part iv. of my series of memoirs in the ' Philosophical Transactions ' I pub- 

 lished a description of a remarkable stem from Burntisland, to which I gave the 

 name of Heterangium Grievii. More recently we have obtained a second and yet 

 more interesting species of the same genus from Halifax. In many respects it 

 agrees closely with H. Grievii, especially in the structure of its central axis and its 

 exogenous zylem-zone. Its distinctive features are chiefly confined to the bark and 

 phloem-zone. In H. Grievii I found no traces of a true phloem, but such a zone 

 is fully developed in the new species, to which I propose to give the name of 

 Pleterangium Tilioides. The vascular zone is abundantly furnished with medul- 

 lary rays of various sizes. The largest primary ones are not only prolonged 

 into the bark as phloem-rays, but as they pass outwards their section assumes the 

 trumpet shape seen in those of the common Lime, the large square, parenchyma- 

 tous cells of which they are composed being arranged in irregularly parallel, arched 

 lines, the concavities of which face the zylem. Between each pair of these primary 

 phloem-rays is a mass of true phloem, through which the numerous narrow 

 secondary medullary rays are also prolonged outwards to the cortex. Longitudinal 

 sections show the phloem to consist of much parenchyma, through which numerous 

 elongated, thin-walled, narrow tubes pass vertically. In tangential sections these 

 tubes are seen to foUow an irregular, wavy course, reminding us of the bands of 

 hard bast in the lime. I detect no evidence of the presence of true sieve-tubes in 

 this phloem, though some of the numerous thin-walled tubes may represent those 

 tissues. 



External to the pbloem-zone are two very distinct zones of cortical parenchyma, 

 in which we discover twin pairs of large vascular bundles passing outwards to 

 what I presume have been foliar organs ; and in the outermost cortical zone we dis- 

 cover large, defined masses of sclerous parenchyma. The plant also exhibits proofa 

 that it also gave off true branches of larger size than mere foliar appendages. 



The vessels vary, from small ones with reticulated semi-scalariform walls in the 

 young foliar (?) bundles, to others of intermediate size in the exogenous zone; 

 whilst the latter conduct to the very much larger ones, which, intermixed with 

 the medullary parenchyma, constitute the medullary axis of the plant. Those 

 of the exogenous medullary regions are unquestionably vessels exhibiting modified 

 conditions of bordered pits. The zylem, phloem, and cortical zones of this plant 

 unquestionably suggest Gymnospermous relationships ; but the structure of the 

 centre or medullary axis has nothing analogous to it among known Gymnospermous 

 plants, recent or fossil. It approaches much more nearly to what we find in the 

 corresponding axis of Lepidodendron selaginoides. 



11. The Multi'plication and Vitality of certain Micro-organisms, Pathogenic 

 and othenvise. By Percy F. Feankland, Ph.D., B.Sc, F.O.S. 



In this paper the author records a number of experiments which he has carried 

 out on the multiplication of the micro-organisms present in natural waters, and 

 also on the vitality of certain pathogenic organisms when purposely introduced into 

 similar media. 



These phenomena have been studied by aid of the method of gelatine-plate 

 cultivation, originally devised by Koch. The first part of the paper treats of the 

 influence of storage in steriUsed vessels, upon the number of micro-organisms 

 present in the unfiltered water of the rivers Thames and Lea, in the waters of these 

 rivers after sand-filtration by the companies supplying the metropolis, and in deep- 

 well water obtained from the chalk. Of these three difierent kinds of water, at the 

 time of collection the unfiltered river-waters are the richest in micro-organisms, 

 containing, as they do, several thousand microbes, capable of being revealed by 

 plate-cultivation, in one cubic centimetre of water, whilst the filtered river-water 

 have this number generally reduced by about 95 percent., and the number present 

 in the deep-well water rarely exceeds 10 per cubic centimetre. 



