* Journal, jin'TimT Micvoscopc Structure of Plants. 31 



of chloropliyll to tliose containing elongated and paler masses ; others 

 containing two rows more closely arranged, and containing from five 

 to ten or more rows of chloropliyll ; smaller fronds branching, of a 

 similar arrangement of chlorophyll cells. 



August 10th. — Similar Algas from the side of a boat taken out of 

 a tidal part of river Lime. 



October 21st. — Specimens of Algfe with innumerable diatoms of 

 various kinds, in which the green cells gradually pass from the square 

 to an elongated shape. Other tubules from the same plant are full 

 of diatoms, having brown cell contents. Tubiiles in which the 

 diatoms have some green and some brown cell-contents, evidently 

 stages of the same plant. 



Nov. 4:th, 1869. — Examined the Alga containing diatoms, various 

 forms of the same plant, single tubules containing rounded masses 

 of chlorophyll, elongated vacuoles containing irregular masses of 

 chlorophyll, double rows of small chloroi^hyll cells. Single rows 

 throwing out branches ; multiple rows throwing out branches ; tubules 

 in which one jiart contains masses of chlorophyll, and a contiguous 

 broken end containing single diatoms, or double cells ; green tubules 

 composed of evident double cells ; crushed portion composed of 

 double cells (green), isolated double cells (green), aggregated trans- 

 parent cell-walls, without chlorophyll. 



The double cells (green) have the same movements as diatoms 

 containing yellow and brown contents. Crushed a portion of one of 

 the larger tubes and found it composed of double cells, having green 

 and light-brown contents, evidently stages of growth of diatoms; 

 watched the movements of diatoms green and yellow in the currents 

 of evaporating water, and found the various forms due to different 

 facets being presented to the view. 



Nov. 8th. — Further examined the diatoms, and found transitional 

 forms from green to brown. Their source in this case is evidently in 

 the cell-walls of the Alga ; some are free within the vacuole, while 

 others appear to form the mass of the Alga, bound together with 

 transparent soridial membranes. 



VI. — The Mode of Examining the Microscopic Structure of 

 Plants. By W. E. M'Nab, M.D. Edin. 



The description of the modes of examining the microscopic struc- 

 ture of plants can best be given by considering each tissue sepa- 

 rately. Let us, therefore, first give a few brief remarks on the 

 tissues themselves ; then proceed to mention the plants best 

 adapted for demonstrating the diflferent tissues, and describe the 

 methods suited to the display of the peculiarities of each tissue. 

 The division of the tissues of plants into the two great divisions 

 of cellular and vascular can hardly be considered sufficient for our 

 purpose, and much confusion results in considering all the tissues 

 of plants as referable to these two divisions. For example, Latici- 



