334 



FOURTH GROUP. SEED-PLANTS. 



five to fifteen or even, according to Schacht, to thirty, in Taxus baccata from five to 

 eight. Continued growth of the adjacent parts of the prothallium gives rise to funnel- 

 shaped indentations in its substance above the archegonia, which in many of the 

 Abietineae are shallow, but in Pinus Pinaster, P. Strobus, and other species are deep 

 and narrow ; in these species each funnel leads do\vn to the neck of an archegonium ; 



FIG. 260. Development of the embryo-sac and archegonia, and fertilisation and formation of the embryo in the 

 Abietineae. / apex of the nucellus of Larix Europaea showing the rudiment of the embryo-sac ; above the sac are two 

 of its sister-cells which are formed with it from a mother-cell, the archesporium ; magn. 430 times. // the young arche- 

 gonium of Abies canadensis soon after the formation of the neck-cell, magn. 150 times. /// longitudinal section of a 

 young ovule of Abies canadensis and a part of the seminiferous scale to which it is attached, magn. 12 times. IV VI 

 Picea vulgaris. /^apex of the embryo-sac with two mature archegonia, magn. 40 times, Vzn archegonium shortly after 

 fertilisation with four nuclei at the posterior extremity of the oospore, of which two only are visible, magn. 50 times. 

 VI the posterior extremity pf the oospore with three tiers of four cells each, and four free nuclei k above it, magn. 80 

 times. VII XII formation of the embryo in Pinus Pumilio, VII, VIII, and X magn. 50 times, IX 30 times, XI 25 

 times, XII 12 times, e denotes the embryo-sac (macrospore), a the central cell of the archegonium, h the neck of the 

 archegonium, / the cavity of the central cell, * the integument,^* the pollen-tube, n the nucellus,./" the seminiferous scale, 

 g vascular bundle, kz the'canal-cell, ka the rudiment of the embryo, k in IV and VI the nucleus of the oosphere, TVS the 

 apex of the root, ivh the root-cap, tthe cotyledons, if the growing-point of the stem, s the suspensor. From drawings 

 by Prof. Strasburger. 



in the Cupressineae (Callitris, Thuja, Juniperus\ where the archegonia are crowded 

 together, the prothallium grows up round the whole group, and thus one funnel is 

 formed which is common to them all, and continues to be covered over by the wall 

 of the macrospore. 



