294 



NATURE 



lAtig. 3, 1876 



living constituents of the vegetable kingdom represent, 

 more or less modified, various successive grades of deve- 

 lopment which plants have passed through. Some of the 

 branches of the family tree have now no living representa- 

 tives, and as to these we must seek for such evidence as 

 palaeontology affords us. To trace out the family tree in 

 all its details must obviously be always a matter of extreme 

 difficulty, and may never be completely possible. Our 

 f resent information does not extend to much more than 



«' 



-4' 



Fig. 7. — Successive stages in development of spores of yeast (after Reess). 



a knowledge of the closely-packed exterior formed by 

 the ultimate twigs. We cannot see very far how these 

 p'jrsue their course, nor get more than an approximate 

 notion of the way in which the main branches are given off. 

 Clearly, however, we may assume that organisms have 

 in the main proceeded from simple and generalised forms 

 to those which are specialised and complex. The simpler 

 existing plants will therefore be the representatives of the 

 oldest forms of all. 



As long ago as 1 836 Endlicher divided the vegetable 

 kingdom into Thallophyta (leafless plants) and Cormo- 

 phyta (leafy plants). The one exhibits the presence, and 

 the other, if we may say so, the absence of the contrast 

 of leaf and stem. Leafless plants are clearly the simpler, 

 and come nearer, therefore, the base of the family tree. 



Now Thallophyta have long been held to fall into two 

 great groups — >1/^<J? (tangles), which, speaking generally, 

 are independent of organic nutriment, contain chloro- 

 phyll, and build up the materials of their tissues from in- 

 organic materials ; Fun^i (thread-plants), on the other 

 hand, are wholly dependent on other organisms, which 

 they feed on, either living or in decay. Each series 

 ranges from the very simplest forms which it is possible 

 to conceive endowed with life, up to others which display 

 a very complicated structure. Nevertheless there is a 

 remarkable structural parallehsm between them, and it 



Zygo- 



FiG. 8. — Germination of yeast-spores (after Reess). 



seems probable that the Fungi do not possess a con- 

 tinuous Ime of descent of their own, but that they 

 are an assemblage of reduced or degraded forms 

 which have abandoned the business of food-manufacture, 

 and appropriate their nutriment more or less ready made, 

 and which correspond to different points in the line of 

 descent of Algae. Thallophyta, therefore, disregarding 

 the cross division into Algee and Fungi may be classified 

 after Sachs,' and mainly according to their reproductive 



J ' Lehibuch der Botanik, 4th ed., pp. 248, 249. 



processes into four classes : — i. Protophyta ; 2. 

 sporeae ; 3. Oosporeae ; 4. Carposporese. 



Protophyta consist of excessively minute plants only 

 visible to the naked eye when aggregated together in 

 considerable masses. They consist of minute particles 

 of protoplasm often no larger than a human red blood- 

 corpuscle or much smaller, which are usually in- 

 vested with a covering of cellulose, sometimes, however, 

 very hard to distinguish. The protoplasm is homo- 

 geneous and without a denser portion or nucleus, but 

 may contain minute particles, and even watery globules. 

 It is either quite colourless or contains chlorophyll more 

 or less masked with other colouring matters. Multi- 

 plication is effected by the fission or bi-partition of the 

 protoplasm of one individual or cell. This frequently 

 takes place in a single direction only, so that the new 

 individuals more or less adhere together in a linear 

 series. The cellulose investment or cell-wall is apt to 

 pass by the absorption of water into a gelatinous condi- 

 tion, which may even form a kind of matrix in which the 

 individual cells seem to be imbedded. Two groups de- 

 serve especial attention, Schizotnycetes and Saccharo- 

 mycetes. Both are destitute of chlorophyll, and so are 

 dependent for their nutriment on materials elaborated by 

 other organisms. In obtaining what they want they set up 

 incidental chemical changes and decompositions. Thus 

 Bacteria bring about putrefaction in fluids containing 

 nitrogenous matters, and yeast produces fermentation in 

 saccharine solutions. 



go 



Fig. 9. — Formation of spores of Mycoderma vtni (after Cienkowski). 



When any fluid capable of undergoing putrefaction is 

 exposed to the air at a temperature of about 30° C, it 

 speedily loses its clearness and becomes turbid and 

 milky. This is usually due in the case of vegetable 

 infusions to the presence of immense numbers of a minute 

 organism known as Bacterium Termo. Other forms are, 

 however, met with, and according to the nature of the 

 fluid, one or other seems to get the upper hand and pre- 

 dominate. They vary in shape from a mere rounded 

 speck (tcwt in. in diameter) to elongated rod-like bodies 

 sometimes rolled into a short spiral. The rod-like forms 

 exhibit free movements which in the larger are obviously 

 due to the presence of a cilium at each extremity, and are 

 probably so in all. 



The life history of the Bacteria is still imperfectly 

 known. One striking kind has been studied from mace- 

 rating pans by Prof. Lankester. It exhibits a great 

 variety of forms, but all are tinged with a peculiar 

 purple pigment, and it seems probable, therefore, that 

 they all belong to the same species, and that the 

 different phases are due to diversities in the condition of 

 development or culture. This, if true, would apply to 

 other series of forms which are colourless or tinged with 

 other pigments. In one condition the Bacterium is in a 

 kind of resting condition ( Fig. i ), and is a mere microscopic 

 spherule of protoplasm. This gradually granulates (Fig. 2), 



