SCIENCE- G OSSIP. 



95 



STRUCTURAL and PHYSIOLOGICAL BOTANY. 



CONDUCTED BY HAROLD A. HAIG. 



Function of Bud-rudiments. — In a note in 

 -" La Nature " for June it is stated that a French 

 •botanist, M. Beille, has recently communicated to 

 the Acadernie des Sciences a paper stating the 

 results he has obtained in the determination of 

 the fate of bud-rudiments in a flower-bud. By 

 xefined histological methods he has been able to 

 trace a connection between the several features of 

 tissues in their embryonic state and those in their 

 adult state, thus enabling him to say whether such 

 and such a bud-rudiment will develop to petal, 

 stamen, or carpel. As is well known, it is not 

 always possible to say, from their relative position 

 on the young floral receptacle, whether a given 

 •outgrowth will become a petal or stamen, as the 

 relations are often changed during further growth. 

 The histological method removes this difficulty. 



Transition from Leaf to Bract-scale in 

 Larix. — A young larch cone in its first stages is 

 hardly anything more than a collection of brilliant 

 red bracts arranged spirally upon a central axis. 

 The rudimentary carpellary scales are microscopic 

 in size, and it is only on cutting sections of the 

 whole cone in the longitudinal direction and 

 •examining them microscopically that- one is able 

 to detect them as very small outgrowths from the 

 main axis, and possibly partly from the upper 



Fig. 1. Transition from Leap to Bract-scale. 



surface of the bract. Each of these bracts con- 

 sists of a central portion or midrib and two lateral 

 " wings." Further down on the main axis we may 

 see structures that resemble the true bracts, but 

 differing from them in that the wings are not so 

 well developed and not so highly coloured. We 

 can, in fact, trace the bract right down to the 

 ordinary leaf, lanceolate in shape, which arises in 

 •conjunction with others from the limited shoots of 

 Larix (fig. 1). The transition is interesting from 

 the point of view of homology, for it gives the 

 carpellary scale more or less the value of a separate 

 shoot, and not only of a leaf -structure, since the 

 scale arises in the axil of the bract, which is of 

 the nature of a true leaf-structure. 



Tannin in Plants. — We find tannin occurring 

 in various plants either in the cortical cells of 

 the stem or root, or in the mesophyll of the 

 leaves. Tannin-cells generally come singly, and 

 may be recognised by the brownish colour they 

 present on sections of the tissue, or by the fact 

 that when treated with solutions of ferrous salts 

 they assume a deep-blue colour. The tannin is 

 probably present in the form of tannates of an 

 •organic base, much as salicin is present as salicy- 

 lates in the various species of Salix. In many 

 cases the formation of this substance gives to 

 plants a certain amount of protection, inasmuch 

 as animals such as snails and many insects will 

 not touch a plant where even a trace of tannin is 

 present. In these instances the tannin is, however, 



usually there in considerable quantities, and it is 

 probable that in those plants where only a few 

 isolated tannin-cells are to be found it occurs in 

 the nature of an occasional excretion — a by-product 

 of some more important chemical process. Tannin 

 forms, however,' an article of food to some or- 

 ganisms, such as Aethalium septicum, "flowers of 

 tan," and therefore cannot always be looked upon 

 entirely in the light of an excretion. It is not always 

 necessary to apply special tests for the detection 

 of tannin, as the sections will, if cut with an 

 ordinary razor, often show the cells already stained 

 a dark-blue colour, due to the action of the iron 

 in the cutting instrument; 



An Interesting Alga. — Whilst examining a 

 preparation of some ordinary pond algae I came 

 across a few filaments of a species of Cladophora, 

 a branched alga, one of the Confervaceae. On 

 separating the filament from the others, and treat- 

 ing first with absolute alcohol to extract the 

 chlorophyll and fix the protoplasm, and then with 

 Schultz's solution, the pyrenoids, which are present 

 in large numbers, scattered all over the cylindrical 

 chloroplast that lines the cell-wall, were easily 

 made out, as were also some peculiar large rounded 

 bodies, each with a smaller body, like a nucleolus, 

 inside it. These structures, which stained brown 

 with the Schultz solu- 

 tion, were presumably 

 of a proteid nature, and 

 were fairly numerous. 

 ■ If these bodies are really 

 of a proteid nature — 

 and there does not seem 

 much doubt about it — 

 we have here in this low 

 form of vegetable or- 

 ganism a formation and 

 storage of proteid mate- 

 rial comparable to the 

 production of crystal- 

 loids and aleurone grains 

 in, seeds, or of proteid 

 reserve in the sieve-tubes 

 of the phloem in higher 

 plants. I could not 

 determine the true na- 

 ture of the nucleolus- 

 like structure in the Fl «- ,?• Single Cell op Alga. 



„ ,, , . , Chlorophyll body contracted, 



centre of the proteid 



hnrlips • hnt it sppmerl to fl > Cell-wall; p, Protoplasm; py, 

 bodies , out it seemea to Pyrenoids ; 5i Proteid bodies ; 

 stain somewhat deeper 

 than the main ground 

 substance. I think I am right in the naming of 

 this analga ; but the presence of pyrenoids rather 

 points to the probability of its being one of the 

 Conjngatae, and not necessarily Confervaceae. 



Leaf Comparisons. — Between the gymnosperms 

 and angiosperms we find many points of difference 

 both in the internal structure and the reproductive 

 processes ; but one of the most striking is that 

 which is presented in the arrangement of the tissues 

 in the " centric " leaf of the gymnosperm as com- 

 pared with that in the usually "bifacial" one of 

 the mono- or cli-cotyledon. There are, of course, 

 instances of centric leaves in the latter, as in 

 Hakea and some others ; but in these we can 

 recognise the more highly developed type in the 

 arrangement and structure of the bundles. In the 

 first place, in the leaf of Pinus or Taxus we find a 

 well-marked central cylinder surrounded by a layer 

 of cells known as the bundle-sheath, or endodermis, 



Pyrenoids ; 

 i, Nucleus. 



