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Show 414 SEXUAL HELATIONS OF PLANTS. ·CHAP. X. ' a d vant ab0'e ov er other plants in their .c ross-·f erctil li·s atiohn b e1· ng assure d . But this ad. vantage Is ga1no In. t e f nemophilous species at the expense of the case o a . f ll . h pro d uct 1. 0n of an enormous superfluity. o· po on,. wit . some risk to them and to onton::~philous Sl~ocws. of theh· fertilisation occasionally fa1hng. I-Ialf the Individuals, moreover, namely, the males,. produce no seed, and this might possibly be a d1sad van tag e. D 1 ·no remarks that dioocious plants cannot sproa<l so e pi d' . f' easily as monrocious and hermaphro 1te spoCJos, or a · ale individual which hapi onecl to roach so1no now Slllb . . . . b I site could not propagate 1ts ]nnd; .but 1t may. e l Ubted whether this is a serious ov1l. Monmcwus ( 0 d' . plants can hardly fail to b~ to a large ext:nt l<DCIOUH in function, owing to the lightness of theu pollen an:l to the wind blowing laterally, with the groat a~ditional advantage of occasionally or often prod uc1nF some self-fertilised seeds·. When they ~ro also. dtchogamous, they a1~~ necessarily clirocious 1n :unctw~L Lastly, hermaphrodite plants can generally produce ctt least some self-fertilised seeds, and they arc at. the same time capable, through tho various means spoCifie.d in this chapter, of cross-fertilisation. 'Vhon theu structure absolutely prevents self-fertilisation, they are in the same relative position to one another as monoocious or dimcious plants, with what may be an. advantage, namely, that every flower is capable of yielding seeds. I CHAP. XI. ' HABITS OF INSECTS. 415 OI-IAPTER XI. Tm: HABITS OF INSECTS IN RELATIO"Y TO THE FERTILISATION OF FLOWERS. Insects visit the flowers of the same species as long as they can _ Cau -e of this habit-Moans by which bees recognise the flowers of tl 1 e same species-Sud(len secretion <,f nectar-Nectar of certnin flowers unattractive to certain insect::!- Industry of bees, and tho number of flowers visited within a short time-Perfol'ation of the corolla by bees-Skill shown in the operation-Hive-bees profit by the l~oles. made by humble-be.es-Effocts of hahit-The motive for porforatmg flowers to sn.vo time-Flowers growing in crowded masses chiefly perfomted. BEES and various other insects must be directed by instinct to search flowers for nectar and pollen, as they act in this manner without instruction as soon as they emerge from the pupa state. Their instincts, however, ar~ not of a specialised nature, for they visit many exotic flowers as readily as the endemic kindR, and they often search for nectar in flowers which do not secrete any; and they may be seen attempting to suck it out of nectaries of such length that it cannot be reached by them.* All kinds of bees and certain other insects usually visit the flowers of the same species as long as they can, before going to another species. This fact was observed by Aristotle with respect to the * See, on this subject, H. MUller, • ~efruchtung,' &c. p. 427; and Su· J. Lubbock's 'British Wi~d Flowers,' &c. p. 20. Muller assigns (' Bienen Zeitung,' June ~87.6, p. 119) good reasons for his ehef that bees and many other Hymenoptera have inherited from some early nectar-sucking progenitor greater skill in robbing flowers than that which is displn. yed by insects belonging to the other Orders. |