THE ANISOTROPY OF MARCHANTIA. 



709 



as regards iheir internal organisation. In the open, with unlimited light on all sides, 

 these shoots grow with their lower surfaces close to the soil, into which the long 

 roots penetrate deeply. Subsequently they produce shoots quite different in shape, 

 long stalks as much as 10 cm. in height, each of which supports either a lobed 

 disc with male organs, or a parachute-Kke structure with female organs. The 

 stalks of these shoots are orthotropic and, when growing in the open, are directed 

 perfectly upright. Transverse sections show however that they are not properly 

 radial in organisation, but have become radial by the rolling together of the two 

 lateral margins of a narrow flat shoot, much as in the case shown at Fig. 398 ^. 

 It is to this that they owe their orthotropism. In the further consideration of 

 this highly remarkable plant I shall confine myself to the two organs referred to, 

 although there are many other things which might be mentioned. If the Marchantia 

 is cultivated— it is very easily reared from spores, or still better from its gemmse 

 ^-on the surface of soil in a 



flower-pot in a room, not too far ^^M 



from a window, the young or- 

 thotropic stalks become curved 

 towards the window, exactly like 

 ordinary seedling stems, and 

 then grow straig"ht on at an 

 angle of about 45°. The flat 

 vegetative shoots on the con- 

 trary behave quite differently : 

 those which have their anterior 

 depressions turned towards the 

 window remain closely appressed 

 to the surface of the soil; those 

 on the contrary whose depressions 

 (in which the growing-points lie) 

 are directed away from the win- 

 dow towards the room, raise 

 themselves from the substratum 

 until they are directed obliquely 

 at an angle of about 45°, so that in this case again the anisotropy between the 

 flat shoots and the orthotropic stalks is approximately at right angles. 



This behaviour was for a long tune quite inexplicable to me, until I pro- 

 posed the question, how would matters be if the Marchantia were made to grow 

 on vertical surfaces of the substratum, with the light falling obliquely from the 

 window ? For this purpose I employed blocks of turf, carefully cut into the 

 shape of cubical bricks and saturated with nutritive solutions, and covered with 

 opaque boxes provided with a pane of glass only on the side turned towards the 

 open sky. A few gemmse were laid both on the horizontal surface of the block 

 of turf, and on the vertical sides — on the anterior face turned towards the light 

 as well as on the two flanks. These were easily retained by the damp sub- 

 stratum and at once began to grow on it. After 2 — 3 months, vigorous and even 

 fructifying plants were produced, and the result of the experiment may be illustrated 



Fig. 401.— (See the text) K the orthotropic conceptacles in which the 

 ^emm£ are produced. 



