SCIENTIFIC NEWS. 73 



a subject of one of its annual prizes, has occasioned 

 the publication of several tracts, the principal of which are 

 those of Link, Treviranus, and Rudolph, all professors in 

 different German universities, Agreeing in most facts with contradicted i« 

 Mirbel, they not only add some observations to his, but sorae P oint$ » 

 contradict him on certain points; which has induced him to 

 publish a defence of his theory, in which he gives it more has defended 

 precision, exhibiting it in the form of aphorisms; while he his the <»?« 

 endeavours to show, that most of the objections arise from 

 his having been misunderstood, or his observations not hav- 

 ing been repeated with sufficient care. 



Mr. Mirbel has likewise presented to the class two pa- 

 pers, one on the germination of the family of grasses, the 

 other on the distinguishing characteristics of the monocoty- 

 ledonous and dicotyledonous plants. 



In the first he shows, that the stigmata of wheat unite Germination 

 in a small canal, which reaches to the base of the embryo; of 8 rasscs « 

 and that the cotyledon, as Jussieu thought, is a fleshy sub- 

 stance, in which the radicle and plumula are imperceptibly 

 developed, and which opens lengthways to let them pass, 

 so that it performs the office of a vaginating leaf. 



From the second it appears, that the cotyledons have Cotyledons 

 great analogy to the leaves, those of the sensitive plant^be- wJ f "ieI»«T 

 ing irritable, of the borages hairy, &c; in short, they are 

 true leaves in the seed. If, when there are two cotyledons, 

 they appear opposite in plants the leaves of which are alter- 

 nate, it is because the stalk cannot develope itself in the 

 seed, and the interval between the cotyledons is not to be 

 distinguished. From the different perceptible analogies be- ■ 



tween them, Mr. M. infers, that the number of the coty- 

 ledons must refer to some circumstance respecting the 

 leaves ; and he imagines, that the monocotyledonous plants Monocotyle- 

 are uniformly those, the leaves of which ensheath each donoUi plaa*»* 

 other. Proceeding to examine the formation of the wood, Wood 

 Mr. M. shows, that it is always composed of filaments in- 

 terspersed in a celjular texture resembling the medulla of 

 the dicotyledons ; but that in many of the monocotyledons 

 these filaments are formed at the circumference as well as 

 jn the centre : the latter in consequence having a double 

 vegetation ; one at the circumference, increasing the dia- 

 meter 



