360 Mr Philip Sewell's Observations wpon the, 



within the first eight to ten days after the expansion of the 

 cotyledons ; it is not, however, the case that all alteration in 

 size or shape takes place within that limit of time. In some 

 cases, even after forty or fifty days, a slight change in shape 

 was noticeable, by which the cotyledons of every species 

 assumed more or less an emarginate character. This might 

 be due to enlargement of cells as distinguished from actual 

 increase in the number of cells composing the lamina ; 

 certainly it was a character assumed at a later time 

 apparently than when the growth of the lamina or petiole 

 was most apparent. 



The growth of the petiole was not noticeable for some 

 days after the time when the laminte had spread themselves 

 out in a more or less horizontal position. The petioles 

 developed simultaneously with the development of the 

 plumule, which in most cases was not to be seen, unless 

 with the aid of the microscope, until ten to fifteen days had 

 elapsed after the cotyledons first appeared above the soil. 



The time which elapsed between the first appearance of 

 cotyledons and the first appearance of the plumule might, 

 however, vary considerably, according to the time of year 

 and the conditions under which the seeds were germinated. 

 Where such facts have been observed they have been 

 inserted, more with a view to future comparison than on 

 account of any suggestions which they afford at present. 



The cotyledons persisted in most species until the leaves 

 subsequently developed cut off their supply of light, or 

 pressed them upon the surface of the ground. Where the 

 subsequent leaves and the cotyledons were very evidently 

 petioled, they persisted for a longer period than was other- 

 wise the case. 



The following table allows of comparison as to the sizes 

 attained by the cotyledons of various of the species when 

 they were mature ; the amount of spread from the top of 

 one cotyledon to the top of the other is also indicated in 

 most cases at its maximum, but as much variation was 

 observed in the latter measurements, we shall refer to them 

 subsequently : — 



