UNI-CELLULAR ALG.E. 



87 



Fig. 17. — Caulerpa denticulata, a monoplastic Siphonean of the natural 

 size. The entire branching primary plant, which appears to consist of a 

 creeping stalk with fibrous roots and indented leaves, is in reality only a, 

 single plastid, and moreover a cytod (without a kernel), not even attaining 

 the grade of a cell with nucleus. 



US to how great a degree of elaboration a single cytod, 

 although a most simple individual of the first order, can 

 develop by continuous adaptation to the relations of the 

 outer world. Even the single-celled primary plants — which 

 are distinguished from the monocytods by possessing a 

 kernel — develop into a great variety of exquisite forms by 

 adaptation; this is the case especially with the beautiful 



