Nov. 28, [889] 



NATURE 



91 



(2) Laige leaves in palms (often 14 feet long), tied in at the 

 leaf-base, e.g. Dii]ymosperinu?n distichum. 



{3) Young buds of many tropical trees hang vertically down- 

 wards, so as to expose the least surface to sun, e.g. Amhenlia 

 iiobilis. 



(4) Prickles ami spines developed, e.g. immense leaf of Victoria 

 7rqia\% 1 rotected from fish, &c., which, in rising from btlow, 

 might nipture the leaf-tissue. 



(5) Patrols of ants attracted. Ants provided with home, 

 honey, and food, e.g. Acacia spharocephala. Similarly, Iponma 

 paniculata attracts ants by racemose glands supplied with defi- 

 nite ducts, two of which are present in each leaf, at junction of 

 blade and stalk. 



(6) During the unfolding and growth of the bud, special 

 mechanisms exist. Thus, water-glands occur at the apex of 

 each leaf-tooth (Saxifraga crustatd), which provide for the 

 escape of the superabundant water sucked up by the root : other- 

 wife the delicate leaf-tissue might be ruptured. In fully deve- 

 loped leaves, on a cold night, drops may be seen escaping from 

 the teeth, e g. balsam {Impatiens Balsamina). 



Other glands are also found which secrete mucilage or resin, 

 and so protect the young structures from the efiects of excessive 

 drought, e.g. ferns {hlechtium Braziliense') and other plants 

 {Clusia sp. and Coprosma .<p.). 



II. — Reproduction. 



The importance of this process is sufficiently obvious from 

 the enormous expenditure of material and energy plants lavish 

 upon it. Ilodgsoitia heterocli'a, an extraordinary Indian climber, 

 with its complicated structure and great beauty, opens for one 

 night only, and shrivels up and falls off the next day. Amorpho- 

 plialtns Pitauum, with its huge inflorescence (the largest in the 

 world), although it takes months to develop, opens only on 

 one night, and then only for a few hours. 



o. — Floruers. 



(1) Contrivances to insure fertilization. Masdevallia muscosa 

 (an orchid) has a sensitive labellum. An insect alighting on it 

 and touching a certain part, is shot into the flower and held a 

 prisoner for some time, 



(2) Protection by means of sticky hairs. Cnphea si'enoides is 

 piotected from the attacks of inse ts by very numerous hairs 

 secreting a gum resin. Many insects are caught, and as many 

 as 7280 may be counted on one plant. 



(3) Plant protectid by ants, but flower fertilized by some other 

 insect. Plumbago rosea has nectaries on the leaves and flower- 

 bracts which attract ants, but the ants are prevented by sticky 

 hairs on the calyx from obtaining access to the honey in the 

 flower. 



5. — Seeds and Fruits. 



Some plants depend upon the enormous quantity of seeds pro- 

 duced— <'.^. the wild carrot {Daucus carota), which, moreover, 

 sows its i-eeds by instalments and at different times. Others — 

 eg. Voandzcia sublet ranea — sacrifice the advantages obtained 

 from a wide dispersal, and depend upon the formation of a few 

 seeds suitably placed in the soil. This plant, in fact, has a 

 mechanism for itself, sowing its own seeds beneath the soil. 



For purposes of distribution, Uminia brevicaulis (a sedge) has 

 its fruit provided wiih small hooks. Small birds, unable to pull 

 out the fruits, are occasionally caught and killed in Jamaica. 

 The fruits of Stipa pcnnata, a grass, bore their way into the 

 ground ; and anuiher species, Stipa spartea, is even liable to 

 bore its way into the bodies of sheep which are so unfortunate 

 as to come in its neighbourhood (prairies west of Red River 

 Colony), 



Contrivances for assisting plants to maintain themselves in the 

 struggle for existence are by no means limited to the higher 

 plants. They exist also in tie Fungi and the Algse, even in the 

 smallest and most microscopic of them. Examples — 



I. Fungi. — Clathrus triscapus, a Queensland fungus, has an 

 orange-red colour, and the spores smell strongly and are em- 

 bedded in a sweet mucilage. Col ur, scent, and sweetness are 

 the usual advertisements used by the higher plants in connection 

 with pollen dispersion. 



Erysphe Alni. The mildew of the alder has wonderfully 

 hooked fruits, which are possibly carried about by tiny /^ra;?, 

 &c. Spores are shot out with some force from the mycelial fila- 

 ments of the fungus, which attacks and kills flies, Empusa 

 musccc. The ergot Claziceps purpurea, at the time of spore- 



formation, secretes a sugary nectar, so that flies are attracted, 

 and eat and disseminate the spores, just as birds do stone fruits. 

 The spores of Scltrotina Vaccinii have an almond smell ; are 

 gathered by bees with the pollen, and, being placed on the 

 >tigma of healthy flowers, infect the ovary and prevent the 

 formation of seed. In the race between the pollen-grain tube 

 (the rightful owner) and the fungus-spore mycelial-tube, the 

 fungus always wins, and soon spreads itself throughout the 

 tissue of the entire ovary, producing mere spores for the bees 

 to gather in mistake again. ■«- .« 



II. Algtr. — The resting-spores of Z?«»/t</!— microscopically 

 small green Alga: — are frequently covered by a spiny siliceous 

 coat. These probably prevent them from being eaten by Anicehc, 

 Phizopods, &c. The protoplasm of certain cells of (Edoj^oniutn 

 ciliatum (a fresh-water filamentous Alga) are in the habit of 

 escaping from the cell-wall and beginning life anew. This pro- 

 duction of the so-called swarm-spore is probably not wholly 

 unconnected with the existence of unfavourable conditions, e.g. 

 Bacteria on the cell-wall, deposits of lime on the cell-wall, &c. 



Mesocarpus sp., r.nother filamentous Alga, carefully protects 

 its chlorophyll plate from too bright light by turning it so that 

 it shall receive the proper amount only. Should external con- 

 ditions be exceptionally unfavourable, the protoplasm of the 

 various cells powerfully contracts, and the filament resolves itself 

 into its vaiious constituent units, which sink to ihe bottom of the 

 river or pond, and there divide up and start afresh. 



Special Points tvorthy of notice. 



(i) Various adaptations by members of the same order, e.g. 

 the Cticurbitaceic (Cucumber family), in the matter of seed' 

 distribution. 



In Schizocarpum fiHforme the seeds escape through a number 

 of slits in the wall of the fruit. 



In Ecbalium elatine the seeds are violently and explosively 

 shot out in consequence of the j^udden rupture of the fruit stalk. 



Sechium edule is indehiscent and contains only one seed. 



Zanonia macrocarpa dehisces at the apex by means of valves, 

 and lets out winged seeds of extraordinary beauty, which, aided 

 by the wind, can cover very appreciable distances. 



(2) Various adaptations by metnbers of the same genus, e.g. 

 the Clerodendrons. 



Clcrodendron Koemferi attracts ants by small glands on the 

 leaf and calyx. 



Clcrodendron fislulosum does the same, but also provides a 

 home for the ants in its hollow stem. 



Clerodettdron cephalanthutn climbs by means of peculiarly 

 modified leafstalks ; has a multiplicity of buds on the axil of 

 each leaf (instead of the usual one) and also possesses glands 

 upon its leaves. 



Such families as this may well be regarded as accomplished, 

 but at the same time their various contrivances are simply sc^ 

 many marks of a cruel and fierce fight. 



(3) Protective contrivances associated with new annual growth 

 and germination. 



Dioscorea, sp. nov., at each new period of growth produces at 

 first inconspicuous shoots with small leaves which are peculiarly 

 modified into climbing organs. When well established and in 

 the possession of a proper support large green leaves appear. 



Hodgsonia hetcroclita, — Here again the shoot on its first ap- 

 pearance is dark purple and inconspicuous, with the leaves present 

 merely as scales. It can then scarcely be seen in the tropical 

 forest. Moreover it is a lateral shoot and not the main terminal 

 shoot which it first protrudes above ground. A second lateral' 

 and the main terminal are held in reserve against possible acci- 

 dent. When it has reached a certain height, it produces the 

 normal large leaves. 



(4) The accumttlation of proactive contrivances in the same 

 individual . 



Blumenbachia Hieronymi. — The flower is at first upright and 

 is fertilized in that position. As the fruit develops, the flower- 

 stalk elongates and the fruit is gradually and gently placed upoi^ 

 the ground. Until quite ripe, it is protected by stinging hairs. 

 Later on, these wither, and the fruit is distributed by means of 

 a second series of grapple hairs, which cling firmly to any 

 passing animal. 



Strophanthus hispidus. — Fruit, when ripe, opens, and lets out 

 a number of magnificent plumed seeds, which are carried by the 

 wind. The hairs forming the plume are sensitive to moisture 

 and dryness, and are each capable of moving through an arc of 

 180°. The hairs spread out in dry weather, so that the seed 



