cultures being designated as the Oakland, Baltimote, and Easton 

 covered stations. The behavior of the plants grown under 

 glass is very different from the behavio-f' of those grown in 

 the open and a description of grwwth as it took place in these 

 covered stations will now be given. 



The cultures grown under glass were placed near the ex- 

 posed cultures at ea^^h of the three places mentioned, so that 

 the climatic conditions for the two would be practically the 

 same except for the effects produced by the glass. That these 

 effects werfi considerable is shown by the very T.arked differ- 

 ences between the plants under the glass and exposed plants 

 growing only a few feet distant. The addition of the covering 

 had in fact as great an effect as would have been produced if 

 the plants had been grown in another part of the st^te. 



Only one of the three climatic conditions dealt with, 

 evaporation, was measured for these covered cultures, and we 

 thus have no exact notion as to what sort of climate existed 

 under the glass. The most that can be done is tD compare 

 the plants of these cultures with the exposed plants and call 

 attention to such peculiarities of the covered stations as 

 seem to be general for all of them. We may be sure, however, 

 that the climatic conditions under the glass differed from 

 the climatic conditions for the exposed plants in certain defi- 

 nite ways. Meaaurements show that the rate of evaporation for 

 the covered stations was considerably greater than for the ex- 

 posed as will be seen by comparing the values given in the tables. 

 We may be certain, also, that some of the incident light was ab- 

 sorbed by the glass and that the light intensity under the glass 

 was thus less than the intensity of the light falling on the 



