428 HOFMEISTER, ON 



In the upper part of the corpusculum the numerous 

 spherical sister-cells of the germinal vesicle are still dis- 

 tinctly perceptible (PI. LX, fig. 13 ; PL LXII, fig. 5). From 

 the fact of their presence* it is impossible that the opinions 

 of Schleiden, Schacht, and Geleznow, as to the process of 

 embryo-formation in the Coniferae can be correct. Accord- 

 ing to the two former the pollen- tube penetrates into one 

 of the corpuscula, fills it up by degrees entirely, and pro- 

 duces the pro-embryo in its lower end, which is pressed 

 against the inner surface of the corpusculum. If this were 

 so, the pollen-tube must pierce through the mass of spheri- 

 cal cells which fills the cavity of the corpusculum before 

 impregnation. Nothing however is easier than to see that 

 those cells are still present when the pro-embryo appears. 

 They are only dissolved very gradually, and become changed, 

 together with the rest of the contents of the upper part of 

 the corpusculum, into a yellowish grumous mass. 



The increase in length of the pro-embryo ultimately rup- 

 tures the base of the corpusculum. A considerable longi- 

 tudinal expansion immediately takes place in the two pairs of 

 cells of which it consists ; this expansion usually occurs in the 

 second cell reckoned from above (PL LXI, fig. 7 ; PL LXII, 

 fig. 8), but sometimes the first expands also. The lower 

 end of the pro-embryo is thus driven deeply into the tissue 

 of the endosperm underneath the corpuscula. The axile 

 cells of the middle portion of the endosperm become in the 

 mean time loosened and softened, by which the course of 

 the continually-descending end of the pro-embryo is pointed 

 out beforehand. The courses of the continually-elongating 

 pro-embryos through the pultaceous mass of the softened 

 cellular tissue, form delicately-winding spirals. 



Soon afterwards the longitudinal rows of cells comprising 

 the pro-embryo become detached from one another. The 

 separation commences at the lower end and progresses 

 from thence upwards (PL LXI, figs. 9, 10). During this 

 breaking up of the pro-embryo into four (very rarely more 

 than four) simple rows of cells, the four shorter cells which 

 formed its upper end which was enclosed by the corpus- 

 culum, become dissolved (PL LXI, figs. 8 10). 



* Observed by Gottsche (' Bot. Zcit.,' 1844, 509), and by Pineau, ' Arm. d. 

 Sc. Nat.,' 3rd ser., vol. ii. 



