198 Transactions 



them in this or in other respects from those of Pan imhecilla. The fragment 

 of one of Hooker's original specimens forwarded to Mr. Cheeseman from 

 the Kew Herbarium agrees perfectly in the form of the flowering-glumes 

 with those collected on the subantarctic islands by Kirk, Chapman, and 

 Aston. In both the Poas under notice the nerves of the flowering-glumes 

 are quite obscure, and it is only by transmitted light that they can be dis- 

 tinctly made out. The two lateral nerves are very close to the edge of the 

 glume, and this added to their obscure appearance makes them difficult 

 to observe readily by reflected light. 



The nerves in the descriptions above referred to are said to be somewhat 

 scaberulous ; but in the large series of specimens I have examined it is 

 very rare indeed for the nerves to be sensibly scaberulous, save on the 

 keel. 



A second differentiating character of some importance consists in the 

 great inequality of the empty glumes in Pon hreviglmnis. My specimens 

 of the entire series (including the two supposed species), both those from 

 the main islands and those from the subantarctic islands, show consider- 

 able variation in the relative size of the empty glumes. In some of the 

 Enderby Island specimens the lower empty glume is almost obsolete, while 

 in quite a number of the Campbell Island ones it exactly matches the lower 

 glume as it appears in the ordinary lowland forms of the series that are met 

 with in the South Island. Moreover, the main-island forms not rarely 

 show as marked a difference in the relative size of the empty glumes as 

 obtains in specimens from the subantarctic islands. 



A third differentiating character mentioned by Mr. Cheeseman is the 

 " acute flowering-glumes " of Poa breviglumis. This character is, however, 

 quite inconstant, and the variations it shows are matched by similar 

 variations in the flowering-glumes of Poa imhecilla. In the original de- 

 scription of the species Hooker describes the flowering-glumes as " obtuse," 

 and later, in the Handbook, he calls them " obtuse or acute." In the series 

 of forms I have been able to study, these glumes are often acute or sub- 

 acute ; but obtuse flowering-glumes occur in the small specimens collected 

 at some altitude on Campbell Island by Mr. Aston. 



In specimens from the main islands and the subantarctic islands alike 

 the panicle is subject to a great range of variation both in length and in 

 form. In small forms only 3 in. or 4 in. high the panicle is short and com- 

 pact, mth shorter and broader spikelets that show smaller, blunter, and 

 more coriaceous flowering-glumes. In other forms the grass is 9-15 in. high, 

 with flaccid leaves and culms, and a panicle that is long, erect or nodding, 

 lax, and ovate-oblong in outline. Others are intermediate in most of the 

 above characters. The lower empty glume is especially variable in size, 

 ranging from an almost obsolete condition to a narrow-ovate acute form, 

 half as long as the upper empty glume, and occasionally even longer than 

 this. 



From what has been said it is evident that the differentiating characters 

 oE Poa hreviglumis are quite inconstant, and that their variations correspond 

 point by point with similar variations in Poa imhecilla. The gradations 

 in the two plants are so complete and parallel that I cannot but conclude 

 that the whole series forms a single species, well marked in general cha- 

 racters, but hardly capable of partition into stable varieties. 



It is possible that the fragment of Poa breviglimiis forwarded from Kew 

 to Mr. Cheeseman does not really belong to that species, a doubt that the 



