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THE AMERICAN MONTHLY 



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fd line. 



radiate form. But throughout the larger 

 part of the order they are what I have 

 termed grouped hairs. Upon the 

 upper side of the leaf they may be 

 grouped only in twos or threes, or the 

 hairs may be even solitary ; but upon 

 the under side of the leaf, or upon the 

 caFyx, the groups will probably con- 

 sist of four, five, six or more hairs, 

 disposed in such a way as to give 

 rise to the so-called stellate appear- 

 ance, although this stellate grouping 

 will often be associated with the sim- 

 pler aggregations, or with the single 

 right hairs. But a tendency to stellate 

 grouping, in some part of the plant 

 or at some stage of its existence, is 

 decidedly characteristic of the Mal- 

 low family as a whole. 



In the genus Althaea there is a dis- 

 position to complexity of form and 

 luxuriance of growth on every part of 

 the plant — even on the petals. 



In Malva there is less complexity 

 of form and less luxuriousness of 

 growth, the stellate groups being most 

 pronounced upon the calyx. 



In Abutilon there is still less hairi- 

 ness and still less tendency to stellate 

 grouping. 



In the genus Hibiscus the hairs 

 almost disappear from the leaves (es- 

 pecially from the adult ones), though 

 the stellate groups still form rather 

 abundantly upon the calyx and the 

 seed-pod. 



These facts are sometimes vaguely 

 referred to in the text-books under 

 the heading of pubescence; but usu- 

 ally Hibiscus is spoken of as smooth 

 or glabrous, because the leaf in its 

 adult stage is hairless, or nearly so, 

 to the unaided senses, while the 

 truth is that hairiness in some part of 

 the plant, in some stage of its exist- 

 ence, and, as a general rule, hairiness 

 of a particular kind, is almost if not 

 quite as much a characteristic of this 

 genus, as well as of its order, as are 

 its " alternate, stipulate leaves and 

 regular flowers, with monadelphous 

 stamens." 



Nothing can be more characteristic 

 of the Borraginaceae, as an order, 



than their hairinesss as seen under 

 the microscope. This is generally 

 of the kind I have described as 

 mammilate ; and so striking is this 

 in almost every genus and species I 

 have examined, that the minutest 

 fragment of a leaf large enough to^ 

 hold a hair, would in most cases be 

 enough to determine at least the 

 order to v/hich it belonged. 



Amongst the Cruciferae, too, there 

 are some very distinct groups of 

 genera marked off by the peculiari- 

 ties of their leaf-hairs, so that one 

 who has once become familiar with 

 Alyssum, Vesicaria, Draba and Arabis, 

 for instance, would have little difficul- 

 ty in determining the place of a speci- 

 men of one of them, by microscopical 

 examination alone. As far as my ex- 

 perience has gone, the grouping of 

 plants by their microscopical charac- 

 teristics has been found to accord in 

 the main with the classifications al- 

 ready made by botanical science on 

 other grounds ; but in running through 

 the order Cruciferje, for example, one 

 is often struck by the wide dissimilarity 

 discoverable by the microscope, be- 

 tween certain groups of genera ; and 

 one is led to wonder whether plants 

 so different in their minute struc- 

 tures can really be near relatives, 

 even though their mode of inflores- 

 cence and some other attributes may 

 be similar. 



Nevertheless, the microscopical 

 characteristics of plants may be 

 determined and tabulated so as to be 

 of much value for purposes of identi- 

 fication ; and I am inclined to 

 think that such labor will some day 

 result in a system by which either 

 extant or extinct orders, at least, can 

 be identified to a certainty ; and such 

 a system would be of no little impor- 

 tance in many lines of scientific in- 

 vestigation, as will at once be seen. 

 Thus, in .geological science, buried 

 parts of plants would throw light 

 upon the age and character of the 

 deposits in which they were found, 

 and in zoological science even the half- 

 digested food of beasts, birds or in- 



