Dr. A. Giinther on Reptiles from St. Croix, West Indies. 209 



when it emerges from this organ it does not measure more than 

 one-third of its ultimate length, although the cells composing it 

 have at this epoch already attained almost the term of their 

 development. 



From these researches it may be inferred that — 



1. From its very origin the radicle is formed of two distinct 

 tissues, both cellular. 



2. That which constitutes the external layer of this organ, 

 and which must be regarded as the first rudiment of a cortical 

 stratum, is susceptible of exfoliation, more or less prompt, ac- 

 cording to the plants, and the temperature and humidity of the 

 medium in which they vegetate. 



3. This exfoliation, which takes place at the apex of the 

 organ, results sometimes in the complete dislocation of the cells, 

 which in this state continue to grow for a certain time in the 

 midst of a viscid matter before being finally thrown off, — some- 

 times in the solution of these cells, in the form of epidermoid 

 strips or cups, often confounded with the coleorhiza. 



4. The exfoliated cells and the substances accompanying 

 them contain, according to the species from which they are 

 derived, substances which appear, when abandoned to the soil, 

 to constitute what have been called the excretions of roots. 



5. The tissue which constitutes the hemispherical extremity 

 of the central portion of the radicle is the seat of the formation 

 and growth of the cells ; these formations take place at first by 

 the binary and quaternary multiplication of cells, which ter- 

 minate the apex of the axis ; and of the cells newly formed, the 

 most external are pushed forward to constitute the exfoliable 

 cortical layer, while the more internal become filled with feculent 

 granules, and subdivide again a little below the apex of the 

 axis of the radicle, attaining there, without any other apparent 

 change, the term of their increase. 



6. The formation of absorbing appendices (hairs) at the apex 

 of the radicle, when it alone is exposed to the contact of moist 

 air, while confirming the existence of a rudimentary cortical 

 layer in that region, bears fresh witness to the tendency of the 

 organism to seek the medium suited to its nutrition. 



XXII. — On the Reptiles from St. Croix, West Indies, collected 

 by Messrs. A., and E. New t ton. By Dr. A. Gunther. 



[With a Plate.] 



A small collection of reptiles made by Messrs. Alfred and 

 Edward Newton in St. Croix (S u Cruz), and presented by them 

 to the Collection of the British Museum, offers a contribution 

 Ann. § Mag. N. Hist. Ser. 3. Vol. iv. 14- 



