246 



KNOWLEDGE 



[NONTMBEE 1, 1898. 



Fig. 1. — Rotifer iuhabiting the hood 

 of a Scale-Moss. (After Kernor.) 



plants which have no true power of digestion are yet bene- 

 fitted by capturing insects ; from the decomposing bodies 

 of their victims products are evolved which the plants are 

 able to assimilate. 



The water-vessels of the Bromelias and allied epiphytes, 

 which often contain half a pint or more of water, are 

 particularly interesting. The hollow leaf-base in some 

 of this group of plants is a veritable aquarium. The water 

 which accumulates in these curious receptacles Fritz 

 Miiller found to be inhabited by caddis-flies, entomo- 

 stracans, and aquatic 

 beetles belonging to 

 species not occurring 

 elsewhere. A small I'rog 

 even takes up its abode 

 among the bromeliau 

 leaves. Species of Utri- 

 cularia also occur — small 

 aquatic plants which cap- 

 ture in their curious little 

 bladders the tiny crusta- 

 ceans inhabiting the 

 water in the bromelia 

 leaves where they grow ! 

 V. mlumhifoUa in this 

 way grows in the leaves 

 of Tillandsias, which are 

 themselves epiphytes on the branches of other plants. 



The term symbiosis is applied to those curious relation- 

 ships in which we find two organisms of different kinds 

 living together in partnership for mutual benefit and 

 protection. A remarkable example of such symbiotic 

 association is afforded by certain rotifers which take up 

 their abode in the pitcher-like leaflets of some Junger- 

 mannias. One of these liverworts (Fiullania dilatata) 

 growing on the bark of species of Acer has hollow 

 appendages of this description in which the water is 

 retained by capillary attraction. In each of these pitchers 

 a rotifer (' 'aUidina stjinhiotka) takes up its quarters, finding 

 in this retreat food and shelter. The association in all 

 probability is one of mutual advantage ; the rotifer is 

 supposed to make a return to the plant for its entertain- 

 ment in the shape of excrementitious products. 



The case of these liverworts and rotifers is particularly 

 interesting in connection with some recent observations 

 made by the writer. In making sections of the chickweed 

 stem to examine the origin of the lateral rootlets referred 

 to in the preceding article, it was noticed that there 

 frequently appeared on the slide specimens of the sHpper- 

 animalcule, Paramrecium, for whose presence it was 

 difficult to account. So frequently did this infusorian 

 put in an appearance that at last the idea suggested itself 

 of its being a regular inhabitant of the water that gathers 

 in the leaf axils of the chickweed. The examination of a 

 number of specimens left little doubt as to the fact of this 

 organism as well as several others frequenting the leaf 

 axils of the plant in question. On submitting water from 

 the leaves of a number of other plants it became apparent 

 that leaf axils are rather favourite resorts for the minuter 

 forms of life. Eotifers or w'^ eel-animalcules, infusorians, 

 monads, desmids, diatoms, micrococci and bacteria are of 

 common occurrence. Paramcccium appeared to be rather 

 characteristic of the chickweed, but was also present in the 

 leaves of the sow thistle. In the leaves of the latter we 

 also found that beautiful, lily-like infusorian the bell- 

 animalcule, Vorticella cyathnia. Eotifer vulgaris occurs 

 more or less frequently in the axils of the self-heal and 

 ox-eye daisy. In none of the leaves examined could ento- 

 xaostracans bo detected, although Cypris and other 



copeopods abounded in jols close to where the plants 

 grew. The absence of th latter may be due to their size, 

 entomostracans being ver much larger than rotifers. 



Although most of thesetrL'anisms are to be found in all 

 sorts of places where rainvater collects, their abundance 

 in the tiny droplets that Irk in the leaf-axils of the plants 

 just mentioned aflfords an nterestmg illustration of how 

 Nature crowds her canva striving to ntUize every nook 

 and cranny that ofifers to ving things the least coign of 

 vantage. 



Infusorians and rotiferfas is well-known, may be dried 

 and reduced to powder wiiout losing their vitahty. After 

 they have lain dormant fc months the addition of a little 

 water at once recalls tha to life and activity. It is, 

 therefore, in the highes degree probable that in their 

 desiccated state they get town along with dust into the 

 axils of the leaves, and -e revived by the water that 

 trickles down into theiiresting places after a shower. 

 St: 1 in the case of the re fers, at least, there is another 

 po- lility. The wbeel-a malcules are exceedingly active 

 litt< creatures. Their Qode of progression somewhat 

 resembles that of the wor s, with which they have close 

 aflSnities. Mr. A. R. Wt ace mentions in hie "Travels 

 on the Amazon " the ren rkable fact that in some parts 

 of Brazil, during the we season, when the lands where 

 they live are flooded, th( 'arge earthworms ascend trees 

 and take up their abode i the hollow leaves of a species of 

 Tillandsia, where they ; ) often found accumulated by 

 thousands. There is th afore nothing at all improbable 

 in the idea that a rotifer ay reach its station in the axil 

 of a leaf, like these Sout \merican worms, by climbing. 



Although only bearing imotely on the present subject, 

 we may recall the case of )sa Banksi.t, Acacia spadicigera, 

 and other myrmecophilo plants where the hollow leaf- 

 bases form the headquar rs of the garrisons of ants by 

 which these plants are d jnded. 



The facts now referrec to go to support the view of 

 Kerner, that in those pl:i s wbtrp aerial absorption ocean 

 the object may 

 be not so much 

 sec u r i t y 

 against 

 drought as to 

 obtain a sup- 

 ply of nitro- 

 genous mate- 

 rials. Both 

 ends are pro- 

 bably attained, 

 for leaves, as 

 we have seen, 

 are capable of 

 assimilating 

 compounds 

 of nitrogen. 

 But whether 

 the absorption 

 take place at 



the roots or at the leave it is evident that contrivances 

 for promoting self-irrigaon are all the more important 

 on account of the nutrive salts which rain-water may 

 hold in solution. 



The prevalence of micr-organisms in leaf-axils suggests 

 a probable origin of the oaiivorous character ; and though 

 it may be diiBcult or tipossible to establish a triJy 

 symbiotic relationship atween any of them and the 

 plants on which they Uvethese observations, nevertheless, 

 touch the threshold of a Jge, inviting subject, practically 

 unexplored. 



Fig. 2. — nimaU inh&biting the aiils of leaves. 



1 and 2,iotifer vulgaris ; 3 and 4, Vorticella ; 



5, aramoeciam ,- 6, Entomo^trecan. 



