VEGETABLE PHYSIOLOGY. 43 



distinct from the acinus, or grain of a compound berry in the 

 raspberry, the seed of the latter having its proper double covering 

 within the pulp. The testa bursts irregularly, and only from the 

 swelling of its contents in germination. 



The hilum, or scar, is the point by which the seed is attached 

 to its seed vessel or receptacle, and through which alone life and 

 nourishment are conveyed for the perfecting its internal parts. 

 Consequently all those parts must be inlimately connected with 

 the inner surface of the scar, and they are all found to meet 

 there, and to divide or divaricate from that point, more or less im- 

 mediately. In describing the form or various external portions 

 of any seed, the hilum is always to be considered as the base. 

 When the seed is quite ripe, the communication through this 

 channel is interrupted ; it separates from the parent plant without 

 injury, a scar being formed on each. Yet the hilum is so far 

 capable of resuming its former nature, that the juices of the 

 earth are imbibed through it previous to germination. 



CHAP. III. 



Generation of Plants. 



It is well known that the ancients supposed two sorts of gene- 

 ration, namely, equivocal and univocal. This latter, they said, 

 took place when any thing was produced from its proper egg or 

 matrix ; the equivocal, when any living thing was generated for- 

 tuitously, or by chance, from the confused mixture of particles. 

 Thus, for example, they believed that % fleas were generated from 

 urine and sawdust ; that myriads of little insects, like atoms, 

 came up out of slimy water, and maggots out of cheese in the 

 summer, that several sorts of herbs quickly sprang up out of 

 mould taken from a considerable depth below the surface of the 

 earth ; and lastly, that worms were produced from putrid carcasses. 

 Others thought that the Creator, at the beginning, mixed seeds 



