Inquiry Into the Structure of Seeds. 23 1 



paneled seed,, had been presented to receive the oxygen gas. 

 Where there is a separate albumen, without any perceptible 

 cotyledons, it is probable that the stalk of the embryo may 

 answer the necessary purpose ; just as the stems of leafless 

 plants must be presumed to perform the usual chemical 

 functions of leaves, though we cannot ascertain in what di- 

 rection the different airs are imbibed or discharged, there 

 being no decided upper or under surface in such stems, any 

 more than in ensiform leaves. Such, however, are rare ex- 

 ceptions, which if not, as yet, found to throw any new 

 light on the subject, certainly do not overturn any important 

 part of the above hypothesis. That some part, immediately 

 connected with the embryo, must be stimulated in order to 

 excite the germination of a seed, this phenomenon being 

 dependent on the vital principle, is evident. I conceive 

 that, when present, the cotyledon or cotyledons are them- 

 selves stimulated by the oxygen gas, or rather by the heat 

 which chemists inform us is produced by the absorption of 

 that gas, so as to set their fluids in motion, and thus to 

 propel the young root and rising plumula. But when the 

 cotyledons are wanting, the embryo may very well be con- 

 ceived capable of sufficient action to imbibe for itself the 

 juices of a distinct albumen, already become milky and sac- 

 charine by the reception of oxygen and moisture, by which 

 merely chemical process, as in barley, so considerable a de- 

 gree of heat is evolved, as must very powerfully excite the 

 vital principle of the budding vegetable. In the few cases 

 where one or more cotyledons and a distinct albumen are 

 together present, it does not seem necessary fhat the gas 

 should act through the former upon the albumen, the two 

 organs being but little connected, and its operation on the 

 latter being independent of all vital or organic laws ; but 

 either the gas itself, or the heat produced, may very well 

 so stimulate the vital principle of the cotyledons, as to pro- 

 pel their fluids into the embryo and assist germination. This 

 opinion is the more probable, as those fluids must be sup- 

 posed more truly of the nature of sap, and more immediately 

 fit for the use of the infant plant, than the liquor of the al- 

 bumen. However this may be, the existence of a cotyledon 

 ». P 4 or 



