102 BOTANICAL GAZETTE. [April, 



sometimes none. Although following closely no rule, thev 

 may roughly be said to occur, if at all, either* in a hvpoder- 

 mal layer or layers immediately beneath the epidermis, or in 

 a line about midway between the epidermis and bundle, but 

 never, in either case, forming a continuous ring. In no case 

 in the sections observed have they been found adjoining the 

 bundle. It must be remarked, "however, that they are not 

 alwavs found in the positions mentioned, but if present in 

 relatively large numbers, the great proportion of them mav 

 be so referred. Apart from these general regions, single 

 cells are found in almost every conceivable position, except 

 adjoining the bundle. They are often found adjoining the 

 respiratory cavities, more often in positions which indicate 

 nothing concerning their function or their relationship to the 

 other leaf tissues. 



In transverse section they show the heavily thickened 

 wall and present the peculiar appearance of "fullness," so 

 marked in the case of this tissue in Pinus (figs. 3, 4 and 5). 



In longitudinal section thev are seen to be elongated 

 prisms with pointed ends (fig" 10), and have the fibrous, 

 banded appearance characteristic of these cells. 



Comparing the development of this "strengthening appa- 



is" of Taxodium with that of Pinus, in which the location 



A 11 /^ • - 



ratus 



of these cells furnishes valuable diagnostic marks, 12 it ap- 

 pears to present the incipient stages of a system which in 

 other sections of the same order becomes highly differenti- 

 ated. In the imperfect annular arrangement of its strength- 

 ening tissue, Taxodium seems to be allied to Taxus on the 



Ab 



prevailing rule that obtains in most leathery' leaves. 13 



In Taxodium, the strengthening cells of the sclerenchv- 

 matous type do not surround the resin duct, or even necessa- 

 rily appear in its region, its support apparently coming from 

 collenchvmatous cells, which here at least seem a transition 

 form between the parenchyma and sclerenchyma. 



In Pinus, on the contrary, the sclerenchymatous strength- 

 ening tissue seems to reach its highest development in its an- 

 nular investment of the resin ducts, an investment which in 

 1 mus sylvestns is in every instance complete and in some 

 cases consists of two layers (cf. figs. 11, 12 and 13). 



The strengthening apparatus of Taxodium distichum dif- 

 fers therefore from that of Pinus svlvestris in the following 

 particulars: (1) In the absen ce of the continuous hvpoder- 



"n« U iwl*2 d Rose ; b °tanical Gazk b. xi. 258. 

 i'De Bary, Coup. Anat. of Phan. and Kerns. 119. 



