September i, 1882.] 



THE TROPICAL AGRICULTURIST. 



263 



as we proceed outwards from this, each successive phase 

 is younger tliau the last. The oldest part appears to be 

 always on the under side of the leaf ; the diseoloration 

 of the upper side and the corresponding appearance of 

 the myceliura there occur later. The appearance of various 

 saprophytic fungi on the old shrivelled spot indicates the 

 completion of the destruction. With these and other 

 phenomena which vary the described courso of the " disease 

 spot " we are not at present concerned. 



The orange-coloured "rust" consists chiefly of small, 

 somewhat reniform boihes, which, from their structure, 

 behaviour towards reagents, tc, and especially from their 

 manner of germination, I have called Credospores, to 

 distinguish them from a second, less common, napiform 

 spore, which presents sufficient analogies to the typical 

 2'eleuto.yjore* of the Uredineie to warrant the adoption of 

 that name also. 



The " Teleutospores " were discovered in Oeylon in March, 

 1880 ;f they occur mingled with the much more numerous 

 Uredospores on the same " rust " patch, and, indeed, spring 

 from the same spore-group. Mr. Abbay seems to have 

 incompletely figured similar bodies, without understanding 

 their nature, on coffee from Sumatra.* Such are, shortly, 

 the external features of the "disease spot," and we may 

 now pass on to the details of form and structure of the 

 parasite itself. 



Since the main facts of development are now discovered, 

 it will be perhaps the simplest plan to trace the history 

 of the adult fungus from the ifredospore — to relate, in 

 fact, what occurs after sowing the spores on coffee, giving 

 the details of structm'e as we proceed. 



The Vredospore {" Sporange " of Abhay and Morris) is 

 figured on Plate I, fig, 1, in various positions, and is 

 seen to be a somewhat kidney-shaped body, broader, and 

 rounded at the free end, and slightly tapering at the 

 other, where it is attached by a very short pedicel to the 

 spore-bearing structiure hereafter described (PI. Ill, fig. 40, 

 c and/). The free ujiper surface is conve-x from before 

 backwards and from side to side, and is studded with 

 small solid papillie. The remainder of the surface forms 

 two converging, slightly flattened sides, which gradually 

 meet beiow in a broad, rounded, saddle-like ridge. This 

 is quite smooth, concave from before backwards, and con- 

 vex from side to side. The vertical transverse section of 

 such a body is somewhat triangular, mth rounded corners ; 

 but various figures are obtained by projecting the several 

 oblique optical sections as it rolls over (Fl. I, figs. \-'6). 

 The upper side alone is normally ornamented, though the 

 papillc'e at times occur on the upper poi'tions of the other- 

 wise smooth sides; these papiiUe ai'e outgrowths of the 

 thick exospore, and are usually pointed and regularly dis- 

 tributed on its free surface (fig. 6 (/). 



The granular protoplasmic contents of the spore are 

 enclosed by a delicate hyaline endospore, which becomes 

 readily seen on germination, or may be detected by such 

 reagents as sodic-chloride, sugar solution, &c. (figs. 6 and 7), 

 which cause it to contract away from the exospore, to the 

 inner surface of which it was before applied (fig. 4). The 

 contents are usually coloured orange red, and at times 

 contain oil drops of an intense orange-red tint (fig. 5); as 

 a rule, however, the granular matrix is uniform through- 

 out in the fresh spore. Under certain conditions the 

 orange tinge is lost, and the contents of the spore become 

 grey and cloudy. With these and other abnormal changes 

 we are not here concerned. The size of these Uredospores 

 averages _^ inch long by -^ broad and deep. 



After lyiug in water for some hours it commonly happens 

 that many of these spores become filled with spherical 

 vacuoles, closely packed in the granular matrix, of equal 

 or unequal size, and varying in number accordingly. A 

 coramou appearance is that figuretl in fig. 7, and the 

 impression of a sac filled with spore-like bodies is suggested. 

 These spherical bodies are, however, not solid, but cavities 

 excavated, so to speak, in the protoplasm, and filled with 

 watery liquid. In the first place they are not constant, 

 but may be .seen to change their position, sixe, iVC, very 

 slowiy ; moreover, they eventually disappear, not by escaping 



• Vide ' Second Report to the Oeylon Government,' 1, 1S80. 

 t f'jiZe'PreliminaryKeport to Ceylon Goverumcnt,' June, 

 ISfO. 

 X Loo. cit., PI. 13, figs. 10, 11 and 12. 



bodily from the sac, but slowly, and this is accompanied 

 by other changes. On crushing the whole carefully, 

 these spheres are no longer seen in the extruded mass 

 of protoplasm. Staining reagents do not colour them darker 

 than the matrix, and they are not rendered clearer by 

 such Huids as would cause contraction of denser protopl.asm ; 

 on the contrary, solutions of sugar, salt, &c., and such 

 reagents as iodine, glycerine, fcc, make them disappear, 

 evidently by the abstraction of water. 



With careful treatment I hav« caused these vacuoles to 

 reappear, after applying weak sugar solution, on washing 

 in pure water. What is the nature of this vacuolisation ? 

 How far is it normal, and how far connected with other 

 phenomena, must be left for future consideration. The 

 proofs that these bodies are vacuoles must, however I 

 think, be admitted. 



The strongest evidence that the papillate body is itself 

 a spore, however, and the basis on which I have chiefly 

 proceeded, is afforded by its germiuation. This occurs 

 in pure water on glass typically as follows. At about 

 two to five, frequently three nearly equidistant spots, the 

 exospore becomes thiuner, and pushed aside by the swelhno- 

 endospore, and a dehcate finger-like tube is protruded 

 from eiich (fig. 8). This tube has very thin cellulose walls 

 and a blunt, rounded apex. It may dilate slightly just 

 beyond the place of exit, and the constriction at that 

 spot is rendered conspicuous in contrast; otherwise the 

 diameter of the tube is equal, and measures about one 

 fifth of the narrow diameter of the spore (fig. 9). This 

 germinal tube rapidly grows forwards, extending, by apical 

 growth, as a simple unbranched cylinder for some time. 

 As it elongates its diameter remains uniform, and its 

 cavity continuous with that of the spore. The orange- 

 coloured granular .spore-contents meanwhile pass along the 

 germinal tube, often presenting a most beautiful streaming 

 motion here and there along their course ; vacuoles and 

 oil drops form both in spore and tube, aud branches are 

 soon put forth at various points, to remain short or become 

 extended, in the same manner as before (fig. 9). This 

 process is, however, limited, and the amount of growth 

 is clearly dependent upon the quantity of food material 

 originally present in the spore.* 



After growing thus for some time with a .sinuous course 

 and uniform diameter the germinal tube dilates, at some 

 place, usually near the growing end, into an ovoid or 

 pyriform sac-like vesicle, into which all, or nearly all 

 the coloured contents soon pass (figs. 12 and 13), leaving 

 the re.st of the tube and spore empty of everything 

 except a few granules and frothy vacuoles. Fig. 11 /'shows 

 in outline what au extensive growth may take place before 

 this sacculation occurs ; it usually occm's sooner, however. 



The pyriform dilation may remain simple, or put forth 

 branching processes here and there from any point (fig. 

 14. Sometimes it grows forwards as a simple tube (fig. 

 15), on which a similar dilatation may arise afterwards 

 and in this case the coloured contents pass forwards into 

 the new vesicle. This forward growth is very rapid, and 

 accomp.anied by vigorous streaming of the protoplasmic 

 contents. It sometimes happens that a septum is formed 

 across the neck of this swelling between it and the rest 

 of the tube (fig. 14). 



Where the branching is rigorous these vesicular bodies 

 may become very complicated, and assume the most gro- 

 tesque figures ; huge vacuoles, streaming, &c., arise as the 

 growth continues (fig. 14). This is not for long, however 

 and though the swellings may remain some hours after 

 the remainder of the tube and spore have rotted, they 

 and their contents become at length the prey of Bacteria 

 Torul.'e, &c. 



On sowing the Uredospores on the lower surface of 

 vigorous liviug coffee leaves, I obtained results in the 

 main similar. The germinal tubes produced, however 

 are usually shorter aud less branched, or quite simple' 

 and the whole process is apparently carried on more 

 energetically. 



At fig. lij is represented a piece of the lower epidermis 

 of a cotyledon of Coffea Arahica, on which Uredospores 

 had been sown some eighty hours ; the spores germinated 

 and p ut forth the tubes fre' iy as described above. The 



* Attempts to grow a i/iore extensive mycelium m 

 nutritive fluids of various kiucis have utterly failed; this 

 is not surprising in the light of what follows. 



