72 



made known intermediate forms also, and he showed that one may 

 obtain such youth and intermediate forms by using as slips shootlets 

 \vhich originate closely above the cotyledons of seedlings. 



In 1890 BEijERiNCK 1 ) was able to add several cases to BEISSNER'S 

 interesting observations. Some of these dealt with the development of 

 branches with youth forms on seedlings after damage by frost, by 

 botanical parasites or by root wounds. In these cases, such branches 

 developed so far away from the cotyledons that without the special 

 circumstances mentioned, normal branches should have developed. 

 BEIJERINCK calls attention here to the significance of such observa- 

 tions for the application of HAECKEL'S biogenetical "Grundgesetz" on 

 the development of plants. 



Other observations dealt with the possibility of having plants retain 

 their youth forms by poor nourishment, for example by cultivating 

 them as potted plants, and BEIJERINCK observed that potted plants 

 are especially suited' for the taking of slips from which "Retinisporae" 

 develop. He presumes that the Japanese originally obtained Reti- 

 nisporae by means of pot cultivations only, i.e., without taking slips. 



Of special note further is BEIJERINCK'S suggestion that the Sereh- 

 disease of the sugar cane, which drew especial attention in those years 

 since it threatened the cultivation of cane in Java, might be consider- 

 ed as a deviation of the branches of the cane with respect to the main 

 stem, such as conifers show with "youth forms" in their branches. 

 More interesting still are the considerations related to the question of 

 Retinisporae, on the possibility, anticipated by BEIJERINCK, of ob- 

 taining dioecious plants from monoecious plants by means of cuttings. 



It is obvious that here also the versatility with which BEIJERINCK 

 treated this subject gave a special stamp to this publication. 



If one called on BEIJERINCK in Delft in the early summer, when he 

 frequently spent many hours in his garden, one was sure of being 

 shown the specimens of Cytisus Ad ami which he had planted there, 

 and which possessed an unusually large number of branches of Cytisus 

 laburnum and of Cytisus purpureus. BEIJERINCK had found, indeed, 

 that if he cut off all branches and made an incision into the main stem 

 of C. Adami, many dormant buds would develop thereon which 

 developed a large number of "bud variants", especially of C. laburnum. 



Of his observations on this remarkable tree, which was observed in 

 1825 by ADAM at Vitry near Paris, and to which BEIJERINCK'S atten- 

 tion was called probably by the study of DARWIN'S works, BEIJE- 

 RINCK has made two short communications. One was published in 

 1900 2 ), the second in 1908 *). When the latter publication appeared, 



! ) L. BEISSNER'S Untersuchungen beziiglich der Retinisporafrage, Bot. Zeitung 48, 

 5 1 7-524 and 533-54 1 , 1 890 ( Verzamelde Geschriften 2, 283-292) . 



2 ) On tin- development of Buds and Bud-variations in Cytisus Adami, Proceedings 

 of the Section of Sciences, Koninklijke Akademie van Wetenschappen Amsterdam 3, 

 365-371, 1900 (Verzamelde Geschriften 4, 48-52). 



3 ) Beobachtungen fiber die Kntstehung von Cytisus purpureus aus Cytisus Adami, 

 Ik-richte d. deutsch. bot. Ges. 26a, 137-147, 1908 (Verzamelde Geschriften 4, 305-312). 



