188 TRANSACTIONS AND PROCEEDINGS OF THE [Sess. L^^IL 



He noticed that the appearance of the radicle and the de- 

 velopment of the cotyledons were the same in light as in 

 darkness. 



G. Ville (Eevue de Cours Scientif., 1865) considers that 

 the action of light is inconsiderable. 



M. Faivre (1879), experimenting with seeds of Trago- 

 'pogon porrifolius, noticed that the seeds developed chloro- 

 phyll and sap more rapidly under the influence of yellow 

 light than under the influence of blue light. 



It will be readily seen, from a perusal of the foregoing 

 resume, that there is no real concordance in the results 

 obtained by the different experimenters. 



There are two serious defects in the methods of experi- 

 ment followed. The first is a failure to secure real identity 

 in the conditions under which the seeds were germinated 

 in light and darkness. Similarity in temperature and 

 moisture is of the most paramount importance ; and though 

 at first sight it might appear easy to secure identity in this 

 respect, it is in reahty a matter of considerable difficulty. 

 The material used as a shield from the light to one of the 

 vessels containing the seeds operated upon, must make a 

 difference in the amount of heat absorbed or radiated, 

 especially if the vessels are surrounded by air, or if they are 

 situated far apart. If similarity of moisture is secured, in 

 the first place, by steeping the seeds for the same length of 

 time in water at the same temperature, this similarity is 

 destroyed during the experiment if the surface of one of 

 the containing vessels becomes colder than the other ; 

 because, in that case, though moisture is condensed on the 

 inner surface of both vessels, the coldest vessel will have 

 the greatest amount of condensation, and the moisture so 

 condensed is derived from the seeds, unless special pro- 

 vision is made to keep the contained air saturated with 

 moisture. The second defect alluded to is the method of 

 judging the progress in germination. The usual plan is to 

 note with as much accuracy as possible the development of 

 the radicle in dicotyledonous seeds, or of the radicle and 

 plumule in monocotyledons. This method is, of course, 

 very crude and uncertain, and much of the variation in the 

 results obtained may be attributed to the employment 

 of it. 



