128 



KNOWLEDGE. 



[Jul 



1901. 



into a deep uanow lioney-well. So far the flower re- 

 sembles 111 inauy respects that of the Salvias described 

 above. But when we look for the stamens and pistil 

 we find an extraordinary structure. The pollen-grains 

 are fastened together into two oblong bundles by means 

 of slender thi-eads, and each bundle is prolonged into a 

 delicate stalk, the tip of which is enlarged and coated with 

 viscous fluid. The whole is embedded in the wall of the 

 flower, over the honey-well, and facing the entrance, and 

 the sticky termination of the stalk alone is exposed. 

 The stigma is likewi.se embedded, and shows a sticky 

 surface below the position of the stamen. How does 

 this structure work? A bee alights on the platform 

 and pushes its head into the entrance to the tube. Its 

 forehead comes in contact with the sticky extremities 

 of the embedded pollen-masses, and on withdrawing, it 

 pulls one or both of these out of the grooves in which 

 they rest: the bee flies off with the pollen-masses sticking 

 on its foi-ehead like two horns. And now a remarkable 

 thing happens. Owing to unequal shrinkage caused 

 by drying, the stem of each pollen-mass curves, so that 

 instead of standing upright they now project forwards. 

 In consequence, when the beo visits another flower, and 

 inserts its head, the pollen-masses come in contact, not 

 with that part of the flower which encloses the pollen, 

 but with the sticky stigmatic surface below, and thus 

 fertilization is effected. The absolute accuracy of the 

 method, the economy of pollen, the way in which the 

 plant is entirely dependent on the visits of the right 

 kind of insect for its fertilization, show that here we 

 have reached the very acme of specialization iu this 

 direction. It is to be noted that along with the modifi- 

 cation of the plants to suit insect-visitors, considerable 

 modification in the structure of the insects has taken 

 place to suit their honey-sipping habits, so that now 

 many are as dependent on the flowers for their food, 

 as the flowers are dependent on insects for their fertili- 

 zation. There is a complete symbiotic interlocking 

 between the representatives of the animal and vegetable 

 kingdoms. 



It is the most highly organized plants that lay them- 

 selves out to attract the most highly organized insects. 

 Simply-constructed flowers like the Buttercups and Um- 

 bellifei-s, which have their honey and pollen openly 

 exposed, are visited by a motley crowd of flies, beetles, 

 ants, and other insects, and these flowers are largely 

 yellow or white in colour. With more specialized flowers 

 come preventive measures, and the encouragement of 

 certain groups of winged insects ; while the most highly 

 developed flowers lay themselves out exclusivelv for the 

 attentions of the aristocracy of the insect world — the 

 bees, butterflies, and moths ; and from the simple 

 yellows and whites of the lower flowers they turn to the 

 richer tones of red, and purple, and blue. 



CONSTELLAT*ON STUDIES. 



By E. Walteh M.\under, f.r.a.s. 

 VI.— THE SWAN AND THE EAGLE. 

 One feature of the primitive constellations, whatever 

 its significance, cannot escape the most casual notice. 

 Many of the forms, indeed most of them, are duplicated, 

 and when thus repeated the twin symbols are, as a rule, 

 not widely separated, but placed close together. The 

 portion of the sky to which we have now come is tlie 

 home of the birds. Here, Ai'atus tells us, 



" Tliere is in front another .Arrow ca-st. 

 Without a bow ; and bv it ilics tde Bird 

 Nearer tlie north. And nigh a second sails 

 Lesser in size, but dangerous to come 

 From ocean when night tlies; the Eagle named." 



In the midnights of early June, the great stream of 

 the Milky Way crosses the sky from due south to due 

 north, not j^assing, however, through the zenith but 

 somewhat to the east of it. Right in the centre of 

 this magnificent arch, forming its very keystone, is the 

 constellation of the Swan, easily found from its neigh- 

 bourhood to Vega, Alpha Lyrae. The figure of the 

 " Bird,' or as we now know it, the '' Swan," may be 

 easily traced out. A long undulating line of bright 

 stars lies parallel to the axis of the Milky Way, skirting 

 the western edge of the great channel which here 

 divides it. This represents the outstretched neck, 

 body, and tail of the flying Swan. Crossing it at right 

 angles, is another undulating line of stars which repre- 

 sents the outstretched wings of the flying bird. The 

 whole constellation has often been termed from its 

 shape the '' Northern Cross." Beta Cygni marks the 

 extreme tip of the Swan's bill, and lies about as far 

 beyond Gamma Lyrae as Gamma is from Vega. Its 

 name is usually given as Albireo, but the meaning and 

 derivation of the word is obscure, and is almost certainly 

 due to a mistake. The Arabic name is Al minkar al 

 dajajah, the " Hen's Beak." It is one of the loveliest 

 double stars in the entire heavens ; the principal star, 

 of the third magnitude, being topaz yellow, the com- 

 panion, of the seve^nth magnitude, sapphire blue, and 

 the distance, 35", being within the power of a field-glass. 



Gamma, the bright star which marks the intersection 

 of the cross, is the centre of a most interesting 

 region. The whole extent of sky from Beta to Gamma 

 is perhajjs the richest in the entire heavens, and Gamma 

 itself is in the midst of rich streams of small stars, 

 interspersed with some strikingly definite dark lanes. 

 Of the transverse beam of the cross, Ejasilon marks the 

 eastern arm, Delta the western, and from Gamma to 

 Epsilon we find one of the most remarkable gaps in 

 the Milky Way, the " Coal Sack," Alpha has been 

 called Deiieb Adige, the " Hen's Tail," or Aridif, the 

 " hindmost " or " follower," both titles appropriate 

 enough to its place. The entire region of the constella- 

 tion is full of interest and beauty, whatever the optical 

 power with which it is examined, from the naked eye 

 up to the greatest telescope. One of the many intei'est- 

 ing objects in the region is Omicrou. To the eye a 

 double star makes a trapezium with Alpha, Gamma 

 and Delta; the brighter of the members of this double, 

 Omicron, in the field-glass will be seen to have two com- 

 panions, one on each side, both of them blue, whilst the 

 chief star is orange. 



Aratus gives the constellation simply as the 

 " Bird," without naming its species, but Eratosthenes 

 defines it as the " Swan," and its length of neck well 

 agrees with the identification. Dr. Lamb's somewhat 

 doggerel rendering of Aratus enlarges upon his author 

 in this connection to bring in absolutely without warrant 

 the story of Leda and Zeus. The second bird is, how- 

 ever, plainly identified as the Eagle, and its chief star, 

 Altair, fomis the third point of a roughly equilateral 

 triangle, the other two angles of which are marked by 

 Vega and Alpha Ophiuchi. It is also easily identified 

 by the two smaller stars. Gamma and Beta, above and 

 below it ; these making with it a characteristic figure 

 of three bright stars in a straight line, on the borders 

 of the Milky Way. The three stars bear the following 

 names: — The middle one. Alpha, is Altair the "Bird," 

 that is the " J''lyer " ; the " Soaring Eagle," as con- 

 trasted with Vega, the '' Swooping " or " Falling 

 Eagle "; the southern star is Beta, Alshain, the " White 



