450 Mr. A. Henfrey on the Reproduction of the 



cleus of considerable magnitude ; and while the embryonal vesicles 

 are produced in the upper part of the embryo-sac, a large num- 

 ber of free cellules are produced in the lower and middle parts 

 (i\iQ endosperm-cells) (PL XVII. F. fig. 8 c). The pollen-tube has 

 here to break through the cellular tissue of the apex of the nu- 

 cleus which clothes the summit of the embryo-sac ; and the em- 

 bryonal vesicle, which becomes impregnated, grows at first into an 

 elongated cylinder {the suspensor) (PI. XVII. F. fig. 7, 8 b), which 

 becomes divided by cross walls into a row of cells, the lowermost 

 of which becomes developed into the embryo (F. fig. 8, 9). This 

 then proceeds in its growth, and in the Dicotyledons is con- 

 verted into the embryo with two cotyledons and a radicle, in the 

 Monocotyledons into one with one cotyledon (or with the rudiment 

 of a second) and a radicle ; in the course of this growth mostly 

 causing the endosperm to disappear by absorption, to make room 

 for it ; in many cases even obliterating the nucleus (in the exal- 

 buminous seeds). In Nymphaa the endosperm is not wholly ab- 

 sorbed, but remains surrounding the embryo,, while the nucleus 

 forms a layer exterior to this organ, so that this plant hasiA 

 double albumen. iir 



The above views are diametrically opposed to those of Schleiden^ 

 who, nevertheless, still maintains his original opinions, and more- 

 over has been supported in an elaborate essay by his pupil 

 Schacht. But the balance of evidence is decidedly against him, 

 and, as far as Orchis is concerned, I am convinced from my obser- 

 vations that he is in error. j3i i 



'^ Gymnospermous Flowering Plants. ' ^"t it^niij^ij 



The remarkable bodies called by their discoverer, Mr. Brown, 

 corpuscula, and the polyembryony, found in the ovules of Coni- 

 fers, have recently acquired great importance in the theories of 

 reproduction, as will be seen presently. The following account 

 of the process of fertilization in the Coniferae is derived from 

 Hofmeister. ^,^5, 



The ovule of the Conifers consists of a short and thick nucleus 

 inclosed in a single, somewhat fleshy integument, leaving a wide 

 micropyle canal open (PI. XVII. E. fig. 1). At the time when 

 the pollen is shed the nucleus consists of delicate cellular tissue, 

 containing deep in its substance an embryo-sac (E. fig. 1 b), formed 

 by the coalescence of a vertical series of a few cells ; Taxus has 

 often three embryo-sacs at first, the Abietinese and Juniperinea? 

 seldom more than one. The pollen-grains pass through the wide 

 micropyle and come in contact with the summit of the nucleus, 

 into the substance of which they send their pollen-tubes. This 

 takes place very soon in Taxus and Juniperus, but not for several 



