2l8 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



darkness, and in part to the absence of the formative influence of 

 light, by which dorsiventrality is wholly lacking from etiolated 

 organs. The reactions of Caulerpa in the dark chamber are to be 

 classed with those exhibited by Ceratofhyllum and Philotria as 

 being entirely independent of pressure, since the reactions in ques- 

 tion are exhibited by isolated floating fragments of shoots. ^^'' 



Duration of Etiolated Organs and Plants. — The actual duration 

 of etiolated organs formed and confined in darkness varies greatly 

 with the degree and mode of development of these organs, and is 

 greatly influenced by the transpiratory relations of the shoot, a sub- 

 ject which will be discussed below. The length of time, or number 

 of seasonal periods through which an ordinary chlorophyllose auto- 

 tropic species may exist, when confined in a dark room, is deter- 

 mined by a number of factors. It is to be said that the data bear- 

 ing upon this subject, as noted in my observations, are by no means 

 to be taken as to express the ultimate endurance of the species tested 

 since a modification of the temperature and moisture to meet the 

 special needs of the separate species would doubtless result in extend- 

 ing the periods much beyond the limits given. If the plant pro- 

 duced in darkness simply the number of stems, branches or foliar 

 organs usually developed in one season, the question became one 

 of the endurance of the separate organs, and the greater majority of 

 the species examined perished with the death and maturity of such 

 etiolated members, many of them being incapable of further exist- 

 ence upon the reduced supply of available reserved food. 



In one series of forms the failure of the earlier organs formed 

 in darkness to reach illumination was followed by the extension of 

 the shoot by excessive elongation of the internodes, and the multi- 

 plication of these members and the dependent branches, in a manner 

 giving an epitome of the life of the normal plant. Thus, in the seed- 

 lings oi AEscuIus, Hicoria and others, the young plantlets developed 

 many more internodes than the normal, the foliar organs of which 

 quickly perished, the entire growth representing a series of efforts 

 to spread chlorophyllose tissues in the light. This capacity in seed- 

 lings in the way of continuous effort, seems to reach its maximum 

 in the cocoanut, which continued a growth of the plantlet for fifteen 

 months without interruption, being nourished saprophytically upon 

 the carbohydrates, fats and proteids, stored in the huge endosperm. 



153 See references to Berthold, Noll and Klemm on page 25 of this memoir. 



