172 Meyen's Report for 1839 on Phtjsiological Botany, 



and therefore the doubling or trebling of the radicular end 

 of the embryo of Viscum cannot be explained as owing to 

 the cohesion of several embryos. 



The structure of the female flower of Viscum is very simple ; 

 it consists of a single bottle-shaped nucleus, which is sur- 

 rounded by a calyx-like organ, from which, at a later period, 

 the white fleshy and gummy matter is produced which en- 

 closes the seeds and represents the pericarpium. In this 

 calyx are inserted the leaves which may be held for petals ; in 

 the male flowers they are metamorphosed into anthers. In 

 Viscum the nucleus is always situated on the apex of the 

 principal or collateral axis ; the end of it receives the pollen, 

 and therefore takes the place of the micropyle ; but in the base 

 of the nucleus is formed the embryo-sac, which grows up- 

 wards into the cavity which has been formed in the nucleus ; 

 and therefore the embryo-sac is not developed in the point of 

 the stalk, as M. Schleiden has stated, but just as usual, in the 

 interior of the nucleus. I could never observe the fecunda- 

 tion by means of pollen-tubes ; but directly after fecundation 

 the embryo-sac becomes divided by means of partitions into 

 a number of large cells, in which, at a later period, the albu- 

 minous body is formed. The embryo remains four or five 

 weeks in the first stage of development in form of a small 

 vesicle in the top cell of the embryo-sac, and when almost 

 all the cells have produced albumen, it increases with great 

 rapidity, and breaks through all the partitions of the embryo- 

 sac from the top downwards. A series of drawings is an- 

 nexed to the Memoir, and will give the requisite explana- 

 tion. 



Towards the end of the year I was fortunate enough to find 

 a specimen of misseltoe which had two embryos in almost 

 every one of the numerous seeds, which germinated very well 

 when laid on the moist window-frame. There were the same 

 number of rootlets as of perfect embryos in the seed, and the 

 embryos were generally a little conjoined at their cotyledon 

 end, but a complete cohesion never took place. The curious 

 position which the embryos in the misseltoe seeds assume 

 when there are several together, may be explained by the 

 growing together of the albuminous bodies and by their pe- 

 culiar form. Each embryo is formed in the axis of its own 

 albuminous body, which at the micropyle end becomes ten or 

 fifteen times thicker than at the lower end; and therefore, 

 when their edges grow together, their axes must form an 

 angle with each other, which varies from 40° to 60°. 



I have also made some remarks on the different circum- 

 stances under which Polyembryony appears. 



