SEED-SOWING. 3 1 



the embryo clears itself from its integuments differs in various 

 species : sometimes it dilates equally in all directions, and 

 bursts through its coat, which thus becomes ruptured in every 

 direction ; more frequently the radicle passes out at the hilum 

 or near it, or at a point apparently provided by nature for that 

 purpose, as in Canna, Commelina, &c. If the radicle has a 

 root-sheath, this is soon perforated by the radicle contained 

 within it, which passes through the extremity, as in grasses and 

 most monocotyledonous plants. The cotyledons either remain 

 underground, sending up their plumule from the centre as an 

 oak, or from the side of their elongated neck as in monocoty- 

 ledons ; or they rise above the ground, acquire a green colour, 

 and perform the ordinary functions of leaves, as in Radish and 

 most plants. In the Mangrove, germination takes place in the 

 pericarp (or fruit) before the seed falls from the tree ; a long 

 thread-like caulicle is emitted, which elongates till it reaches 

 the soft mud in which such trees usually grow, where it speedily 

 strikes root and separates from its parents. Trapa natans has 

 two very unequal cotyledons ; of these the larger sends out 

 a very long petiole, to the extremity of which are attached 

 the radicle, the plumule (or young stem), and the smaller 

 cotyledon. Cyclamen germinates like a monocotyledon; its 

 single cotyledon does not quit the seed till the end of germina- 

 tion, and its caulicle thickens into a fleshy knob which roots 

 from its base. The Cuscuta, which has no cotyledons, strikes 

 root downwards and lengthens upwards, clinging to anything 

 near it, and performing all the functions of a plant without 

 either leaves or green colour of its own. In monocotyledons 

 the cotyledon always remains within the seminal integument, 

 while its base lengthens and emits a plumule. In Cycas, 

 which has two cotyledons, the seminal integuments open and 

 the radicle escapes." (Lindley.) 



From the ' Flore ' we learn that two chemists of the Academy 

 of Brussels, Messrs Deheian and Ed. Landrin, have made some 

 interesting discoveries relative to the germination of seed. It 

 is well known that the action of the air and the presence of 

 water are necessary conditions ; but hitherto the mode of action 

 of these two agents has not been fully understood. MM. 

 Deheian and Landrin have been enabled to throw some light 

 on these mysterious phenomena. It is now ascertained that 

 the effect of water is to soften the covering of the seed so as to 

 render it permeable by gas. When they have imbibed sufficient 

 moisture, the tissues of the seed acquire the property of con- 

 densing gases. This condensation cannot take place without 



