22 



KNOWLEDGE, 



[January 1, 189G. 



"Fia. 5. — Transrci'sp section : D, Doiltlei- stem ; 

 n, st-em of liost ; .Tt/, xyloiii (wood); p/i, pliloi'iii ; 

 c, cortex ; p, pitli ; .n/', ph', xylem and pbloem 

 of haustoriiim ; .17/", ph.", tlie same of host stem. 



In Fig. 4 is shown a part of the stem of a plant around 

 ■which a dodder has wound itself; A is the stem in question, 

 (/ the stem of the dodder, and / its ilowers. Fig. 5 is a 

 section of the same stem, and shows the maimer in which 

 the dodder lias fastened itself to it. It may he noted in 

 passing that when the Cimmta seedling comes in contact 



with dry, innu- 

 tritions support, 

 it does not twine 

 itself about it, 

 although, as Von 

 Mohl ' notes, the 

 same plant would 

 encircle tightly 

 the stem of a 

 nettle, for in- 

 stance, in nine 

 hours. There is 

 an obvious ad- 

 vantage in this, 

 as in dry weather 

 the support 

 would absorb 

 water fi-om the 

 slender stem. 

 When the Cus- 

 ciita has once 

 iiecomo attached 

 to a nutritive 

 support, it may afterwards twine round a support from 

 which it can derive no nourishment. At frequent intervals 

 in the close spiral where the stem is brought into intimate 

 contact with the support, small lenticular protuberances 

 make their appearance. The origin of these can be 

 studied by making a number of sections through that 

 part of the stem. 



Through the thin- walled papillate epidermal cells a 

 ferment is excreted, which attacks the ei^idermal cells of the 

 plant around which the Cuscuta is entwined, and ultimately 

 dissolves them. While this is going on the haustorium 

 is increasing in size ; it dissolves its way through the over- 

 lying cortical parenchyma until it reaches the exterior. 

 Then it passes into the host-plant by the entrance already 

 prepared for it by the epidermal cells, and proceeds 

 towards the centre of the stem. It eats its way through 

 the cortical cells of its host by means of a ferment secreted 

 by its elongated apical cells, the material of the dissolved 

 cells furnishing it with fresh supplies of nutriment. This 

 provides the cells situated behind the apex with energy, 

 that enables them to increase in size and then divide up. 

 In this manner the haustorium increases in length ; the 

 dissolution of the host-cells and its own elongation pro- 

 ceeding simultaneously. Should the vascular bundles of 

 the host be far apart the haustorium grows into a medul- 

 lary ray, and then develops to a greater extent laterally 

 than apicilly, and so applies itself to one of the bundles. 

 Should the bundles be pretty close to one another it grows 

 equally on both sides, and thus attaches itself to both 

 bundles. This is what has happened in the specimen 

 figured (Fig. 5). The phloem of the haustorial bundles 

 (/)/(') has attached itself to the phloiim of the host-bundles 

 (pli") at X, and the xylem of the haustorial bundles (xi/) 

 has united with those of the host (.ry") a.t X. 



There are many points of interest in connection with 

 the relations existing between the dodder and its host, 

 the recounting of which would take us beyond the limits 

 of this paper. 



* " Annuls of Botany," A'ol. viii., p. 75. 



THE FACE OF THE SKY FOR JANUARY. 



By Herbert Sadler, F.R.A.S. 



SUNSPOTS and faculfc are still to be observed in con- 

 siderable numbers on the solar disc. Conveniently 

 observable minima of Algol occur at llh. 12m. 

 P.M. on the 14th, 8h. Im. p.m. on the 17th, and 

 'Ih. 50m. P.M. on the 20th. 



Mercury is an evening star, but is too near the Sun to 

 be seen during the lirst portion of the month, and after- 

 wards his great soutlicrn declination somewhat interferes 

 with observation. On the 11th he sets at 5h. 13m. p.m., 

 or about one hour after the Sim, with a southern declina- 

 tion of 21° 7', and an appai-ent diameter of 5}/', -Yu'ij^hs of 

 the disc being illuminated. On the 21st he sets at Gh. 8m. 

 P.M., or one hour and a quarter after the Sun, with a 

 southern declination of 15° -10', and an apparent diameter 

 of 6^', TBa^li^ of ^^^ "^'sc being illuminated. On the 

 31st he sets at Gh. IGm. p.m., or about one hour and 

 a quarter after the Sun, with a southern declination of 

 11° 2', and an apparent diameter of 8|", T^.l'^ths of the 

 disc being illuminated. He is at his greatest eastern 

 elongation (18i°) on the 25th. While \isible he describes 

 a direct path through Capricornus to the confines of 

 Aquarius. 



Venus is a morning star, but is rapidly diminishing in 

 brilliancy, and her great and increasing southern declina- 

 tion rather militates against her successful observation. 

 On the 1st she rises at 4h. 21m. a.m., or about three hours 

 and three-quarters before the Sun, with a southern decli- 

 nation of 17° 3', and an apparent diameter of 18", y'Vi'jths 

 of the disc being illuminated. On the 11th she rises at 

 4h. 45m. A.M., or 3h. 20m. before the Sun, with a southern 

 declination of 19° 44', and an apparent diameter of I65", 

 ^/jths of the disc being illuminated. On the 21st she 

 rises at 5h. 7m. a.m., or 2h. 50m. before the Sun, with a 

 southern declination of 21° 13', and an apparent diameter 

 of 15f", yVo*''^s of the disc being illuminated. On 

 the 31st she rises at 5b. 25m. a.m., with a southern 

 declination of 22° 0', and an apparent diameter of 14f", 

 three-quarters of the disc being illuminated. During 

 January she describes a direct path through Scorpio into 

 Ophiuchus. 



Mars, Saturn, and Uranus are, for the observer's pur- 

 poses, invisible. 



Jupiter is a resplendent object in the evening sky, being 

 in opposition to the Sun on the 25th. On the 1st he rises 

 at 6h. 5m. p.m., with a northern declination of 1U° 8', and 

 an apparent equatorial diameter of 45f". On the 11th he 

 rises at 5h. 19m. p.m., with a northern declination of 

 19° 28', and an apparent equatorial diameter of 46',". On 

 the 21st he rises at 4h. 32m. p.m., with a northern declination 

 of 19° 48', and an apparent equatorial diameter of 46^". 

 On the 31st he rises at 3h. 42m. p.m., with a northern 

 declination of 20 ' 8', and an apparent equatorial diameter 

 of 46^''. At the beginning of the month he is about 

 1° N. of S Cancri, and continues a retrograde path 

 through Cancer during the month, passing through the 

 outlines of the scattered cluster Pr^sepe. The following 

 phenomena of the satellites occur before midnight on the 

 days named, while the planet is more than 3° above and 

 the Sun 8° below the horizon : — On the 1st an eclipse dis- 

 appearance of the first satellite at 8h. Gm. 41s. p.m., and 

 its occultation reappearance at lOh. 57m. p.m. On the 

 2nd a transit egress of the shadow of the first satellite at 

 7h. 44m. P.M. ; and its transit egress at 8h. IGm. p.m. On 

 the 3rd a transit ingress of the shadow of the second 

 satelUtc at lOh. 9m. p.m., and the transit ingress of the 



