1502 Journal of Applied Microscopy 



CURRENT BOTANICAL LITERATURE. 



Charles J. Chambeki_\ix. 



Books for review and separates of papers on botanical subjects shotild be sent to 



Charles J. Chamberlain, University of Chicago, 



Chicago, 111. 



REVIEWS. 



Hill. A. W. The distribution and character of -j^j^i^ |^^. y^^ ^111. constitutes 



connecting threads in the tissues of /t»us r r . 



..-. .t vv.''v-f "and other allied species. Phil. Part I of an extensive study by Gardi- 

 Trans. of the Roy. Soc. of London. Ser. B.. ^er and Hill of " The Histolog\- of the 

 194: 6^-125: pis. 31-35. iQOi. °' 



Cell Wall, with special reference to the 



mode of connection of cells." The purpose was to discover the extent and 

 distribution of the connecting threads in any particular plant. The embryo and 

 seedlings of Pinus pirwj and the mature tissues of Pinus syh-cstris were chosen 

 as particularly favorable material. The endosperm was also studied in P. pirua. 

 The endosperm consists chietiy of rather large, rounded cells, but a close 

 examination shows that in many cases an internal division has occurred. The 

 threads are evenly distributed in the young walls, but are grouped in the older 

 walls. Near the cot)ledons the cells are smaller, the threads thicker, and there 

 are traces of ferment action. Ferments from the cot}ledons pass into the endo- 

 sperm through the threads, and by the same route, food materials pass from the 

 endosperm to the embr)-o. 



In the seedling the absorptive side of the cotyledon is more abundantly sup- 

 plied with threads than the side not exposed to the endosperm. There are no 

 threads in the external walls of the epidermis, and but ver)^ few connecting the 

 guard cells with their neighbors. All parenchyma cells show a general resem- 

 blance in the character of their threads, the threads on the end walls being 

 irregularly scattered, while on the side walls they are grouped. In the phloem, 

 all the sieve tube threads show a characteristic median dot. The albuminious 

 cells at the edge of the phloem of the leaf have their threads grouped in localized 

 thickenings on the walls, and serve to pass materials from the mesophyll to the 

 phloem. The ver}- numerous threads of the root cap form a connection with the 

 free surface of the root and with the periblem. 



In the mature tissue of P. sylvestris the threads in the cortical tissue are 

 similar to those of the seedling. In the phloem there is no connection between 

 the sieve tubes and the bast parenchyma, or the starch medullary ray cells. The 

 sieve tube threads on the radial walls have a median dot. The torus of the 

 bordered pit is probably traversed by threads which soon disappear. In the leaf. 

 the distribution is about the same as in the cotyledon. The endodermis. with 

 ver)- numerous threads, is in close connection with the cortex and the stele. In 

 the pericycle, living cells are connected by threads, but there is no connection 

 between the pericycle and the lignified transfusion tissue. 



In general, the main direction of threads in the cortex and phloem is tangen- 

 tial. The transiton," nature of certain threads explains the absence of threads 

 between the sieve tubes and medullar)- ray cells. Except in the medullar)- rays. 



