SENSITIVE PLx\NTS 



develop in the spring (as the famihar hawthorn of 

 the hedgerows) are red and brown. The colts- 

 foot which throws up its flower-bearing stems in 

 February or March, well before its leaves, also 

 clothes its flower stalks with reddish-coloured 

 scales, and many other examples might be quoted 

 where early growth takes place and, consequently, 

 all the available heat of the sun's rays is needed. 



This copper colour, then, is but another proof 

 of the delicacy of the leaves of the Wood-sorrel 

 family, and it is an additional indication of the 

 sensitiveness of their leaflets and how much they 

 need protection. A species that has evolved and 

 developed a detail of this kind until every leaf has 

 become a deep copper colour is, of course, a pro- 

 gressive one ; in this species, too, the sleeping move- 

 ment is much more readily induced than in the 

 common British species. Furthermore, there are 

 other species of oxalis which, with a little rough 

 handhng, will droop their leaflets in broad day- 

 light ; and in the Oxalis sensitiva, of India, we 

 have another example of the same genus which 

 has evolved its sensitiveness to almost the same 

 stage as those of the Mimosas, or true sensitive 

 plants, for its leaves contract at the slightest touch, 

 just as shown in the figured representations of the 

 sensitive plant. Also, we may note that amongst 

 the Mimosas themselves all the species close 

 their leaflets as night comes on ; and amongst 

 the various species we find exhibited every grada- 

 tion of sensitiveness, just as we do in the Wood- 

 sorrel family. 



F 65 



