848 REPORT— 1901. 



TUESDAY, SEPTEMBER 17. 

 The following Papers were read : — 



1 . Heter agenesis in Conifers. By Dr. T. P. Lotsy. 



I am going to give a demonstration of a very interesting fact which is called 

 heterogenesis by Korschinsky in a lengthy paper which, originally published in 

 Russian, is now published in German in the last luimber of ' Flora.' 



Heterogenesis, mutation, and spontaneous variation are all words for the same 

 meaning, but the interesting fact about them is tiiat they seem to form at least 

 one way in which new species can arise. I am first going to show you one 

 of the original specimens of Capsella Heegeri, kindly given to me by Professor 

 Count Solms-Laubacli. You will all have read his paper on this subject in the 

 ' Botauische Zeitung,' and so I have only to remind you that this species was 

 discovered in Lindau by Professor Heeger, in the midst of a large community of 

 Capsella bursa pasturis, and there can be very little doubt that this species has 

 suddenly arisen from Capsella bursa pastoris. I need not remind you of the fact 

 that Capsella Heegeri is true to seed : it reproduces Capsella Heegeri, and does 

 not revert to Capsella bursa pastoris. 



Much more elaborate work, though on the question of the origin of species by 

 means of spontaneous variation, has, as you all know, been done by Hugo de Vries, 

 wlio is just publishing his important ' Mutationstheori(\' 



I need not remind you of his results, especially witli Oenothera Laynarchiana , 

 which species he cultivated for more than fifteen years, and of which he obtainetl 

 a number of new species, all suddenly arisen. In his book he calls attention to 

 the fact that a species apparently can exist for very long periods without ever 

 forming new species by means of sudden variations, and that then a period may 

 come during which that .species does form new species. If this is true, it goes 

 without saying tliat species wliich are in the period in which they form .spontaneous 

 variations should be observed very carefully, and it is therefore that I want to 

 call your attention to two genera of Conifers which are in a period of spontaneous 

 variation, a period in which they do form mutanta, to use the terminology of 

 de Vries, which mutants majj be true to seed. I do not say that they are, as the 

 plants have not yet produced any. 



The first species is Cuprcssus Laivsoniana. Among a large number of seedlings 

 at least one plant arose which was very different indeed, as you see here — the 

 Cupressus Lawsoniana Jf7«sf-?«— and among another lot one which was more 

 ditierent yet, the Cupressus Lawsoniana hicopodioides. The first one arose in the 

 horticultural establishment of v. d. AVessel in Esse, aud the other in that of 

 V. d. Elst in Dedemsraart, both in Holland. I do not hesitate to say that these 

 plants, if their common origin were not known, would be described as true 

 species. 



The other plant I want to show you is Thuja occidentalis SpaetJii, which arose 

 in the same sudden way in the horticultural establishment of Spaeth in Rixdorf, 

 near Berlin. 



While I do not want to state that the plants here sliown ai-e new species, I 

 yet dare say that a careful observation of these two genera at as many difi'ereut 

 portions of the world as possible may well be advised, and this is the sole object 

 of my communication. 



I should think that especially Cupressus Laiosoniana is worthy of a good deal 

 of regard in this respect, more so than Thvja occidentalis in fact, Inasmuch as I 

 feel confident that the new forms of these two species have nothing to do with 

 ' .Tugendformen,' while perhaps some retinospora question might step in in the case 

 of Thuja occidentalis Spaethi. 



