EUCALYPTUS MICROTHECA. 



importance for building purposes, on account of the paucity of Eucalyptus-species of tall growth 

 in those wide tracts of country ; and it is further of significance, that E. microtheca will brave 

 a climatic temperature as torrid and as high as any on our planet, the thermometer rising in the 

 shade, on places where this Eucalyptus grows, occasionally to 127° F. For the vigorous develop- 

 ment of this tree, it seems however necessary, that some humidity should exist beneath the surface 

 of its localities. This species has evidently not received the attention, which it merits, for 

 accHmation or rather translocation ; in future forestral measures, likely to be adopted also for the 

 great desert-regions of Africa, it is probably destined, to play an important part ; its ratio of 

 growth seems not yet recorded anywhere. 



The leaf-stomata of Eucalyjotus microtheca are amphigenous ; their number is nearly as 

 large on the upper page of the leaves as on the lower ; hence they are called for this and for 

 numerous other species similarly circumstanced isogenous in the present work ; this almost equal 

 distribution of the stomata coincides with the similarity of the color of both sides of the leaves ; 

 whereas the occurrence of stomata on the lower sides of the leaves only (hypogenous stomata) 

 indicates a disparity also otherwise of the two leaf-pages, the upper being darker and often 

 shining, the lower paler and frequently without lustre, while moreover in these latter cases the 

 leaves are not by a twist of their stalks placed in so vertical a position as those with isogenous 

 stomata, and are indeed generally turning more in a horizontal direction. Species of Eucalyptus 

 with solely hypogenous leaf-stomata are considerably less numerous than those with amphigenous 

 stomata, and they belong largely to cooler regions, while such Eucalypts as are bearing great heat 

 and much dryness present leaves with isogenous stomata. Among the species with amphigenous 

 leaf-stomata are however very many, which have on the upper side of the leaves a much lesser 

 number of these breathing organs than on the lower side. This distribution has been 

 characterized as heterogenous in this work, and pertains also to some species inhabiting regions 

 with less heat and dryness. Nevertheless among the Eucalypts with isogenous stomata are 

 comprised also several kinds, which do not advance into torrid climes naturally, though some 

 power of adaptability to the influences of dry heat seems indicated by this location of the 

 breathing pores irrespective of the structure of the latter. In some forms (not always specific) of 

 the genera G-eijera, Atalaya, Canthium, Carissa, Jasminum and Tecoma the writer of this work 

 observed, that in cooler humid forest-tracts their leaves are dark-green on the upper side and much 

 yalei on the lower, while in arid shadeless regions the leaves show almost as pale a hue on the upper 

 page as on the lower, comparable to the differences in this respect between E. corymbosa and 

 E. terminalis. Considerable diversity is shown as regards the size of stomata by various 

 Eucalypts ; thus E. clavigera, B. Cloeziana and E. setosa have them several times smaller than 

 E. alpina, E. globulus and E. incrassata. Two years ago Dr. A. Tschirch in an able treatise on the 

 development and structure of stomata (Garcke's Linnasa xliii. 139-252) alludes to a few Eucalypts 

 also, and illustrates so far E. incrassata (figure 12) and E. obliqua (figure 14). Some references 

 in this important essay to the climatic location of E. amygdalina were however recorded from 

 erroneons information, that' species in a marked manner belonging to humid forestral regions 

 solely, never occurring in any open arid tracts, its stomata therefore indicating no particular 

 adaptability of the foliage to resist great heat combined witli much dryness. 



Eucalypts are prone to form offshoots from stumps, especially if the felled trees were not of 

 verj' great age ; but this mode of renovation takes places in different kinds of Eucalyptus not 

 with equal force or readiness. Comparative observations on this subject are not sufficiently 



