1855.] Linnean Society. 367 



from its integuments, and produced by the expansion of the obtuse 

 extremity of the radicle, which he calls the " gommo ;" and Gaudi- 

 chaud the radicular bulb. This view was taken by Turpin nearly 

 twenty years ago, and represented by him, in the germination of 

 Solanum tuberosum (Mem. Mus. xix. p. 19. t. 1), where all the radi- 

 cular portion of the embryo is referred to the tigelle or ascending 

 system, while the true root is represented as beginning from its 

 sprouting point in the radicular bulb. It has not, however, been 

 generally countenanced, and Mr. Miers states that he cannot per- 

 ceive that it has any advantages over the more generally received 

 theory which regards the radicle as an elementary root, commencing 

 from the point of union of the cotyledons and their junction with 

 the plumule. On the contrary, it is disproved by numberless facts, 

 and more especially by one to which he lately called the attention 

 of the Society, in the germination of the embryo oi Xanthochymus , as 

 figured by Dr. Roxburgh ; in which (in addition to the principal root 

 thrown out at the base of the seed, at the point which Dr. Allemao 

 would call the radicular bulb) another secondary root is seen pro- 

 ceeding from the summit of the nucleus out of the ascending collar 

 or tigelle, immediately below the scales, which appear to be minute 

 cotyledons, showing that the main body of the nucleus or radicle 

 belongs to the descending system of the root. It is more natural, 

 Mr. Miers thinks, to conclude, in the case cited by Dr. Allemao, 

 that the main descending shoot, growing out of the radicular bulb, 

 and also the subsequent coleorhizal rootlets, are productions of that 

 axile portion of the radicle, which Mr. Miers has called the neorhiza ; 

 and under this point of view he considers it easy to account for the 

 coleorhizal character of the secondary rootlets in the germination of 

 Ceratocephalus, as described by St. Hilaire. A verj' singular example 

 of this sort of production is shown by Klotzsch, in the germination 

 of the seeds of Pistia (Ueber Pistia, Berl. 1853, plate 1. f. C.D.E), 

 where the many secondary rootlets, or branches of the neorhiza, 

 force their way through the epirhizal covering of the main root, ex- 

 tending it as a coleorhiza, in the form of a long cylindrical tube, 

 which at length breaks away, leaving a long sheath in the form of a 

 thimble, covering the extremity of each growing rootlet, and which 

 probably thus performs the functions of a spongiole. 



