202 MM. Garreau and Brauwers on Cell -formation, Growth, 



attention of botanists, in 1850, to the excoriation and the mode 

 of increase of the radical fibres of the hyacinth, and the viscous 

 thickening which is observed at the extremity of young adventi- 

 tious roots of willows; but while the figures he gives of the 

 objects represent faithfully what occurs at the seat of the elon- 

 gation of the tissue, this is not the case with that part of his essay 

 which refers to the elementary formations of these organs, since 

 he states them to arise from an extra- cellular cambium. More- 

 over, the objects to which this botanist directed his investigations 

 were too limited in number, and the conditions of the experi- 

 ments were not sufficiently varied, for anything like a profound 

 study of the subject. It may be added that in science, whatever 

 the object attempted, it often happens that interesting facts 

 escape even the most patient observers ; and it may be imagined 

 that, notwithstanding the merit of the author just cited, our 

 researches are justified by the hope of adding some new facts to 

 this important question. 



For the greatest facility and success of observations of the 

 facts relating to the cellular formation and growth of the radicle, 

 it is of great importance to trace its development in the absence 

 of contact of any foreign body capable of adhering to or affect- 

 ing its surface. With this view, selected seeds of very diverse 

 species were placed, moistened with rain-water, upon hair-sieves, 

 and covered with a moist woollen cloth. These seed-beds, 

 placed in pots which contained water at the bottom, kept the 

 seeds in a constantly moist atmosphere; thus the radicles, 

 whose development proceeded more or less rapidly according to 

 the temperature (which could be adjusted at will), formed tufts, 

 beneath the meshes of the sieve and above the surface of the 

 water, in which the subjects of observation, equal in age and 

 dimensions, afforded means both for multiplied examinations 

 and control of the observed facts. 



Seeds placed in these conditions germinated much more 

 quickly, at equal temperature, than in the best-prepared earth, 

 — a result which appears attributable to the free access of air. 

 Thus, at a temperature of 78° F., the radicle of cress was pro- 

 truded from the seed-coats in eight hours, those of Camelina in 

 fifteen, and from the caryopsis of little millet in two days. 



When the radicle begins to sprout, it is usually smooth all 

 over its surface, and presents no mark of exfoliation when the 

 germination takes place in the ordinary thermometrical condi- 

 tions of the atmosphere in the climate of Lille ; but at a tem- 

 perature of 68° to 78° F., the exfoliation begins very early in 

 plants with feculent perisperm or cotyledons; and this more 

 pi-ecocious tendency to exfoliate coincides, as we shall soon see, 

 with a peculiar mode of dislocation of their elementary organs. 



