376 Cooke and Schively on Observations on the 



tuber, it has formed a distinct row of epidermal cells along 

 its front. A root sectioned just before its emergence from 

 the tuber was seen pushing out the tissue of the tuber as a 

 great swelling (Plate XXX, Fig. i). There were but two 

 more rows of cells left to be penetrated, and these were just 

 being split off at one end by the pressure. A distinct space 

 intervened between the newly formed epidermis of the root- 

 tip and the double row of cells lying beyond. 



In somewhat older tubers, where the roots have attained 

 to some length, there is still a considerable area of embryo- 

 nic cells at the tip of the root. This area is cone-shaped, 

 its base lying across the root-tip. It consists of small cells, 

 with a large nucleus and densely stained cytoplasm. 



In none of these earliest stages is there any trace of the 

 formation of a root-cap. This endogenous origin of the 

 structures called grapplers by Schrenk, establishes their 

 morphological nature as true roots, though undoubtedly 

 they are very degraded ones. 



Comparative Histology of the Flowers. 



Many interesting facts are revealed by a detailed compari- 

 son of the evident or chasmogamic and the cleistogamic 

 flowers. They are clearly constructed on the same general 

 plan, but are modified so as to function differently. One 

 flower represents the original primitive condition in struc- 

 ture, though it shows a great loss in vigor in the present 

 state of the plant. The other flower illustrates the reduction 

 and degradation that may accompany parasitism. The cleis- 

 togamic flower is an admirable example of structural modi- 

 fication to suit definite function ; it also shows to what an 

 extreme the reduction of flower parts can be carried, while 

 there is still abundant production of seed. 



The Calyx. — This is identical in structure in the two flower 

 types. It is synsepalous and shows five evident lobes. Five 

 bundles traverse the calyx, one ending in each lobe. These 



