352 



MESSRS. CTEIL WEST AND H. TAKEDA ON 



occur in tlie phloem (PI. 35. fi^. 17); they are in direct organic connection with the 



sieve-tubes of the rhizophore-stele. 



3. Arrangement of the Moots. 



The arrangement of the roots in Isoetes has already been described by Von Mohl 



24, p. 183), Hofmeister (16, p. 358), Scott and Hill (28, pp. 428-4^30), Stokey 

 (32, p. 315), and Lang (20, p. 784). 



However, a reinvestigation of this question, which was greatly facilitated by the large 

 dimensions of I. japonicay has led us to put forward an entirely new interpretation. 



The corm-lik 



dex of Isoetes is perennial, and may live for very many yea 



The 



annual increment in the number of roots is very larare indeed; Hofmeister (16 p. 359) 

 states that as many as six generations of roots may be produced during the vegetative 

 period of one year. Moreover, the duration of each root is far less strictly limited to any 

 definite period than that of the leaves, which persist for one season only. Thus it 



Text-fig. 9. 



Text-%. 10 



2 



Diagram showing arrangement of the first six roots 

 of a young plant of Isoetes jaiionica. The roots are 

 numbered consecutively. 



Diagrammatic transverse section of the caudex of 

 Isoetes japonica, showing the order in which the roots 

 are differentiated. Compare text-fig. 11. 



follows that a very considerable area is required for the attachment of these numerous 



roots. 



The roots are borne upon a specialized structure, the rhizophore, which in th 

 must be regarded as an organ sui generis. 



I 



the 



very young 



sporophyte, the first three roots, when fully developed. He 



along the centre line of the three lobes of the caudex repectively (text-fig. 9) 



It 



however, be remembered that the caude 



ylindrical 



of the very young plant is roughly 



state of affai 



the lobing of the caudex shown in the diagram does not represent the 



The fourth, fifth, and sixth roots lie alonsrside the first, second 



and third respectively (text-fig. 9) 



Even in the very young sporophyte, the primary 



meristem of the rhizophore can easily be distinguished at the base of 



th 



group 



of 



