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PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION

On applying Kleiss’ oil-immersion lens to the specimen illustrated by fig. 44, newphenomena were brought to light. I had already obtained some faint glimpses of twoor three delicate threads springing from some of the pointed murications of the spinesin such specimens as fig. 41, and which threads appeared to lose themselves in theinvesting plastic substance. In the specimen now under consideration we find thatsuch threads are but the commencements of a very complicated system which permeatesthe plastic substance in every direction. I was long inclined to believe that thesebranching threads anastomosed to form a regular network. I noticed that whenevertwo of them met there was a small but very decided apparent thickening of the tissue,visible even when the threads themselves were almost invisible ; but later observationseach have led me to conclude that such is not the case, but that they merely start fromeach pointed mucro as at fig. 44, a, a, a, and spread through the plastic substance by asuccession of dichotomous divisions. It is scarcely necessary to say that the structures,a, a, a, of fig. 44, represent the free portions of spines that have been intersected asthey pass through the plastic element a little above the outer surface of the capsule-wall, but similar threads are given off from the upper surfaces of the branchingtubes, a,', a'.

I have already pointed out that in the more matured spines, as in fig. 47, a', wefind the mucronate projections of specimens like fig. 44 also converted into branchingtubes. This condition is well represented by fig. 50, where three of the spines are seenintersected transversely, whilst a fragment of a fourth appears in its longitudinalaspect. All four spines demonstrate that the mucronate projections, with their divergentthreads of fig. 44, are here replaced by freely branching tubes which radiate in everydirection. I have examined the section from which this figure is taken to see if Icould discover any anastomoses between the separate sets of branching tubules; butI have failed to do so. In all the cases where such anastomoses appeared to exist, itbecame manifest that separate branches merely overlaid one another.

I think there can be no doubt that the branching threads of fig. 44 are identical withthe branching tubules, h, h, of fig. 50. If so we must assume that the former is theirundeveloped condition, whilst in the latter they have not only attained, but have evenpassed their maturity. Fig 50 represents them in the most perfect form in which Ihave yet found them; but it is obvious that the branches, 6, 6, of that figure are butthe truncated bases of what were at one period much more extended ramifications.Wherever we see into these truncated branches, we find open mouths of thin-walledcylinders, as at b', b\

It appears to me most probable that the external capsule-wall indicated in all thespecimens figured by the letter a, is a cellulose exosporal membrane, which has beenprolonged into numerous radiating branching tubes, the secondary branches of whichvery closely resemble those figured by Van Tieghem and Le Monnier in their‘ Recherches sur les Mucorinees but having their ramifications more multiplied and* ‘ Annales des Sciences Naturelles,’ 5 e serie, Bot., tom. 17, plate 20, figs. 12 and 13.