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106 MISSOURI BOTANICAL GARDEN. 



peared in the old locality. Besides, the interest was centered 

 in the seedhngs obtained from a small amount of seed gathered 

 in the fall of 1906 on green-petaled plants in Bellefontaine 

 Cemetery. In the spring all seed was sown in sterilized soil. 

 The seedlings which appeared were first transplanted to a 

 flat, which was placed in the screenhouse.* Forty-four seed- 

 lings in all made their appearance. One of these died. The 

 remaining 43 were transplanted just at the time when they 

 commenced to flower. With one exception, all bore the 

 green-petaled flowers. There was but one plant which bore 

 yellow flowers. Already in its earliest stages it could be dis- 

 tinguished from the others by its darker, somewhat brown- 

 ish foliage. How to account for this plant is difficult. 

 Insufficient sterilization of the soil is a possibility which can 

 safely be excluded. Numerous control experiments have 

 proven this. Besides, had such been the case, seedlings of 

 other plants might have been expected to make their 

 appearance. There remain two possibilities. Either the 

 plant is the result of a cross or the seed was accidentally 

 mixed at the time of collection. At least another year will 

 be needed to settle this question with any degree of cer- 

 tainty. 



Engelmann, t in his classical treatise on plant teratology, 

 distinguishes two classes of virescence. By virescence in the 

 narrower sense he understands those cases where an organ, 

 losing its color, becomes green though retaining its original 

 form. Under frondescence, on the other hand, he classes 

 those cases where organs, while retaining their position, ac- 

 quire the character of leaves. To the latter phenomenon, 



* This screenhouse, composed of a wooden frame, into wliich panels of 

 fine wire screen are fitted every spring, and which possesses a glass roof, 

 I use for the purpose of excluding insects from those of my plants which 

 do not readily lend themselves to protection from insect visits by means 

 of parchment paper bags or portable screen-cages. It is especially useful 

 in the cross-fertilization of very small flowers, where the operation is liable 

 to be long and tedious. It allows the potted plant to be elevated to a 

 convenient height and eliminates all danger of insect visits during the 

 operation. 



t Engelmann, G. De Antholysi Prodromus. 32. Frankfurt a. M. 

 1832. Reprinted in "The Botanical Works of the late George Engelmann." 



