35 



The above description refers to the floating leaves. There 

 are, however, thin, bright green, submerged leaves produced 

 by Brascnia, which I noticed and reported some years ago. 

 They grow at the base of the stem in hmited number (I never 



■ 



found more than two or three on the same stem). In outline 

 they resemble the floatmg leaves, but they are not longer than 

 one inch, usually much smaller. Their blade is quite thin com- 

 pared with that of the floating leaves, consisting of only four 

 layers of cells. The upper and lower epidermis both have flat 

 cells with wavy outlines. Both are, of course, destitute o( breath- 

 ing pores, but the lower epidermis is provided with very small 

 water-pores at the margin, also with hairs like those on other 

 parts of the plant. The assimilatory layer, under the upper epi- 

 dermis, has oval cells, elongated parallel to the leaf surface ; the 

 chlorophyll occupies the lower and upper horizontal walls. Chlor- 

 ophyll grains are also seen in^ the other layers, especially in the 

 third, which is a very much reduced spongy parenchyma. The 

 conductive tissue is likewise only poorly developed, but slender 

 annular vessels and very narrow leptom elements can be plainly 

 distinguished. 



Of the peduncle I will only mention that it possesses three 

 mestom bundles, each of which, however, has only one leptom 

 group and only one intercellular (hadrom) canal, all o( the latter 

 facing the center of the peduncle. 



Every collector, no doubt, has found it a rather difficult task 

 to prepare good herbarium specimens of Brasenia, on account of 

 the thick layer of mucilage that coats nearly all the parts of the 

 plant in contact with the water, causing it to adhere to the drying 

 paper.* As I do not know of any published investigations in 

 reference to this mucilage, permit me to state my observations as 

 to its origin and nature. If we examine the epidermis of parts 

 which are in contact with the water, we find it thickly beset 

 with hairs. I counted as many as 560 on one square mm. of leaf 

 surface. On the older parts of the rhizoma and the stems the 

 hairs occur neither in such abundance nor are they as active as 

 on all the younger organs, especially the growing apex of the 



* To obviate this difficulty I placed the fresh specimens between sheets of mush'n, 



from which they can be detsiched niuch niore easily when dry thwi from paper, 



