268 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



normal development being most marked in the tissues ordinarily- 

 carrying on the photosynthetic functions. The facts secured in the 

 investigations furthermore disturb many currently accepted conclu- 

 sions. Among these is " that growth in breadth is in all cases hin- 

 dered or prevented by darkness," '^^ since it has been found that the 

 leaves of man}' species, principally monocotyledonous forms with 

 parallel veins, do attain a width equal to the normal, of which 

 Hyacmt/ms, A^ara'ssus and Tipularm are examples. Sachs and 

 other workers have found a width less than the normal in leaves of 

 Narcissus and Hyacinthus, but in the etiolative experiments de- 

 scribed in this volume the leaves were flattened mechanically until 

 the laminae were in a plane when the measurements taken gave the 

 above results. It seems justitiable to conclude that the amount of 

 growth and development achieved by an etiolated leaf may be de- 

 pendent to some degree upon the degree of development which these 

 organs have made during the formation of the bud in which they are 

 enclosed, a consideration to which Sachs has previously called atten- 

 tion. In this instance the full effect of etiolation might be obtained 

 only by the culture of the plant for a second season in continuous 

 and complete darkness. If this condition is taken into account it is 

 doubtful if any plant develops leaves of either normal length or 

 width in darkness. So far as the records are available the hypopodial 

 region of the leaf is least affected by etiolation. The bract-like 

 leaves of Asparagus, the small leaves of Bowica, and the leaf-bases 

 of AEscuIus attained a size in darkness not less than that in light. 

 Then the stipules of Apios and Populus did not suffer any marked 

 reduction as a result of etiolation. The broad leaf -bases of Smilax 

 were similarly resistant to the reducing effects of etiolation, although 

 the tendrils arising from these bases were markedly affected. So 

 far as the activit}- of the cells is concerned the processes of division 

 and multiplication as well as actual enlargement of the elements in 

 various forms has been found to go far beyond the normal in many 

 instances, and it is evident that no part of the behavior of the leaf 

 may be attributed to the direct action of illumination upon the cells, 

 but that organs react as a unit to whatever forces constitute the dom- 

 inant factors in producing the abnormal forms characteristic of etiola- 

 tions. 



Etiolation of Flowers and Inflorescences. — The greater number 



181 Vines, S. II. Physiology of Plants, p. 3S1. 1886. 



