284 



the ground, or to a low height; one can readily obtain shoots which entirely take the form of the young 

 foliage. (See also Planchon's and C. de Candolle's remarks at Part LII, p, 89. J.H.M.). It sometimes 

 happens that without any appreciable injury one sees branches appear on a tree -which take on the 

 appearance of the juvenile stage, and form by this means a curious contrast to those which surround 

 them. This retrogression towards anterior forms, and which is like a partial rejuvenation of the tree, is 

 not an obstacle to the flowering; these branches of juvenile aspect sometimes flower and ripen the fruits 

 as well as those of the adult form." 



(See also Part XLIX, p. 273, J.H.M.). He goes on to say :— 



It would be desirable for the describer of Eucalyptus if the two groups of Biforms and Uniforms 

 were clearly determined ; unfortunately it is not the case. Between the extremes of each group, between 

 the most Uniform and the most Biform Eucalypts, one finds a numerous series of species, where these 

 differences taper off in a very gradual manner, so that one does not know where to place the limit of 

 separation. On the other side, when we see how unstable almost all the characters are, on which we try to 

 found a species (my italics, J.H.M.), we ask ourselves if there are not some common to the two groups, 

 distributing indifferently their individuals amongst the Uniforms and the Biforms. It is a question which 

 presents itself to our mind when one has before one seed-plots where certain species are represented by 

 very numerous specimens. One is struck then by the slight uniformity that they present, without being 

 able to attribute it with certainty to a mixture of different seeds, or to bad labelling. It is not impossible 

 that seeds of the same species collected from different individuals give more or less dissimilar results. 

 Finally, though one has no proof of it, it happens that the crossing of neighbouring species or of simple 

 varieties of the same species are the first and principal cause of these variations. (Naudin, Mem. i, 349). 



He subsequently writes, reviewing the general subject : — 



First Foliage. —It is very variable in a single species, changing in shape with age and tending to 

 take the same form and exhibiting the same appearance in a very different species according as the trees 

 approach their adult age, which causes me to repeat that the foliage must be observed in its successive 

 phases. "What is called the jumviile state of Eucalypts often furnishes useful characteristics for 

 distinguishing species. 



In Eucalypts the leaves are sometimes opposite, sometimes alternate. There are some in which 

 they remain opposite during the whole life of the tree ; in most cases, however, they are only opposite in 

 the first period of their development, then they give place to alternate leaves. This first period, or juvenile 

 stage, lasts for a greater or lesser length of time, according to the species, which justifies in a certain 

 measure the qualification of biform species. Finally there are many others in which the leaves are always 

 alternate, except the six or eight which immediately follow germination. These species may then be 

 called uniform, and they are so at least relatively. However, even in their case; the leaves of the first stage 

 often differ more or less from those which characterise the adult stage. Based on these diversities we 

 may divide the EucalytJts into three groups or sections : — 



1. The uniform opposite-leaved, 



2. The uniform alternate-leaved, and 



3. The biform, 



but I hasten to observe that these three groups arc not always clearly defined, and there are some cases in 

 which one has difficulty in deciding if such species should be ranged with the uniforms or biforms. (2nd 

 Mem., p. 9.) 



Naudin then makes the following apologia for that classification of species 

 which he submits. His Biforms and Uniforms (with otherjmaracters) take part in it, 

 and he points out that only few species are concerned, namely, those he has under 

 cultivation in France. I have translated some additional remark's in his admirable 

 pamphlet : — 



Classification of Species. — Descriptive botanists have often employed the dichotomous method for 

 facilitating the recognition of species, especially in genera where they are numerous. This method is 

 excellent, but it presupposes that the student has before him specimens on which he can find all the characters 



