General Notes. [February, 



GENERAL NOTES. 

 BOTANY. 1 



An Instance of the Physiological Value of Trichomes. — The 

 tissues of nascent organs are thin-walled, have a relatively large 

 amount of protoplasm; and are gorged with nourishing sap. While 

 in this condition they possess no air passages or cavities, and the 

 stomata are consequently incapable of performing their function 

 — they can no more "breathe" than can an animal with its lungs 

 full of water. This formative period in the life of the tissues, how- 

 ever, is one in which a rapid supply of oxygen is required to 

 carry on the metastatic changes incident to growth. This need 

 is supplied by greatly increasing the surface of the organ bathed 

 by the air, allowing a greater transfusion of oxygen through the 

 uncuticularized surface walls. The expansion is secured by means 

 of innumerable slender trichomes. 



These trichomes are thus seen to be a provision for increasing 

 the absorbing surface, to the end that abundant material may be 

 supplied for metastasis. 



As the tissues mature, the intercellular spaces beneath the 

 stomata with their extensions ramifying throughout the organ 

 become empty of sap and allow of the free circulation of air, while 

 the cuticle becomes nearly or quite impervious. The oxygen- 

 ation of the tissues is then more readily effected through internal 

 communication; the hairs therefore disappear or are replaced by 

 those serving a different purpose. — % C. Arthur. 



The Arrangement of Fibrous Roots.— A few years ago, in 

 harvesting about fifty bushels of beets of several varieties, my at- 

 tention was drawn to a peculiarity in the arrangement of the fibrous 

 roots of which till then I had been unaware. While the greater 

 part of the beet was nearly or quite bare of rootlets these were 

 very numerous and closely clustered in two vertical bands on op- 

 posite sides of the main root. Each band covered, say, one-tenth 

 of the entire circumference, more or less. Later I observed just 

 such an arrangement of the rootlets of turnips. But this year I 

 have seen some turnips with the fibers in simple rows as in carrots 

 and parsnips. In these last the rootlets are in vertical (or now 

 and then somewhat spiral) rows. The number of rows seems to 

 be always four, but so situated as in some degree to correspond 

 with the two bands in beets and turnips; that is, the rows are not 

 exactly equidistant, but arc, as it were, arranged in two pairs on 

 opposite sides of the main root, and vet so nearlv equidistant that 

 it is sometimes difficult to say which two constitute a pair. The 

 intervals between the rows are commonly in the ratio of 5 to 7, or 

 on a cross section the lines joining the rows would form a parallelo- 

 gram whose sides would be about as 5 to 7. 



The rootlets of carrots differ from those of turnips and beets in 



