Chapter X —153— Drosera 



condition in the gland cells supposedly in a state of repose, he found 

 all possible conditions. It should be here noted that various authors 

 had previously described the resting condition in various ways. Darwin, 

 ScHiMPER, DE Vrees, Bokorny, Goebel, Akerman thought that in 

 this condition the gland cells have a single large vacuole. Gardiner 

 described the gland cell as consisting of a fine meshwork of protoplasm 

 holding red sap in the interstices. Dufrenoy held a similar view, be- 

 lieving that there are many small vacuoles. Quentanilha found a 

 meshwork of threadlike vacuoles. Allowing for discrepancies of under- 

 standing it is obvious that Homes' findings bring these various views 

 into some harmony, since no one condition prevails in the resting gland 

 cells. 



Having compared living and fixed material it was established to 

 Homes' satisfaction that his fixative (osmic acid, 2%, i part; mercuric 

 chloride 2.5%, 4 parts) preserved the cell structure accurately. Know- 

 ing also that the glands in the middle of the leaf are more active in 

 secretion than those standing along the limb (since the inhibiting 

 action of the environment on the former is less effective), he made a 

 statistical study of the gland cells as to the form of the vacuome. But 

 a statistical study called for standard conditions. These were supplied 

 by growing plants under three sets of conditions, inciting minimum, 

 medium and maximum secretory activity. From these plants Homes 

 obtained evidence of the behavior of the gland cells under these various 

 conditions, and found that, though all states of activity occurred in all 

 cases, there was a preponderance of one state over the others in any 

 one experimental set of conditions. Relying on the relative abundance 

 of the different structural states of activity, four '' witness" glands 

 were chosen to serve as criteria, called types A, B, C, and D. Briefly 

 stated, and neglecting details, the outer glandular cells of these types 

 have vacuomes of the following character: 



T5T)e A. the vacuome consists of a single large vacuole. 



Type B. — — — — numerous small droplets. 



T3T)e C. — — — — fewer, larger droplets. 



Type D. — — — — a thicker reticulum. 



It was then found that glands at minimum, medium and maximum 

 secretory activity displayed the above cytological characters in the 

 following percentages: 



showing clearly that when glands are at minimum activity, the 

 glandular cells are in the state in which they have a single large vacu- 

 ole, while when in maximum activity, the vacuome is a thick reticulum. 

 Intermediate conditions characterize glands of approximately medium 

 activity. In the second layer there is a similar course of events, but 

 these are not so pronounced, and do not follow the changes of the outer 

 layer promptly, scarcely ever doing more than fragmenting the 

 vacuole into two or three parts. The cells of the parenchyme bell (the 



