46 



ACADEMIC BOTANY. 



is no ovary, style, nor stigma. The open micropyle (Fig. 

 47, C, m) secretes a fluid on which the pollen-grain is held 

 when the wind bears it to the ovule. Here it germinates ; 

 then it sends out a tube (Fig. 47, B, ps\ which, as we know, 

 is a prolongation of the intine, and which contains the 

 fovilla, or nourishment (19). The extine, as we have al- 

 ready learnt (20), has no special openings provided for the 

 emission of the pollen-tube; it bursts irregularly. We 

 see in the Pine pollen-grain a trace of the prothallus of the 

 Cryptogams (Fig. 47, B, y) ; here it is a small cell cut off 

 from the true or pollen-cell. We know also (20) that 

 the process of both fertilization and fruit-ripening is very 

 slow. 



78. The Joint-Firs, or Sea-Grapes, are low seaside plants 

 with slender, jointed, green-barked branches destitute of 



foliage, except the minute 



leaves at the joints. The 



flowers now have bracts 



, which sometimes simulate 



a perianth ; but 



each flower is 



still nothing 



more than a 



naked ovule. 



Fig. 48. — Joint-Fir, or Sea-Grape (Ephedra diatachya). A, T'Iiiq }ioq fwn 



malefla. B, female fls,, which grow in pairs. C, a pair of fe- -■-"'* "do^ LWU 



male fls., showing the 2 naked ovules, each with an erect style- cOatS the inner 



like process, which is a prolongation of the tegmen. , ' . 



(tegmen) pro- 

 longed into a slender .process resembling a pistil ; but the 

 process is open at the apex, so that the ovule is still naked 

 (Fig. 48, A, B, C). 



79. The Welwitschia belongs with the Joint-Firs. It is a curious 

 dwarf tree of Southwestern Africa. The trunk or stock (Pig. 49) rises 

 but a few inches above the ground. It has two long, ribbon-like leaves, 

 evergreen and parallel- veined, like the leaves of Endogens (Monocot- 

 yledons). These leaves are the cotyledons, put forth when the seed 

 germinates, and persistent through the lifetime of the plant, which 

 is estimated at one hundred years. The leaves are 3 feet wide and 6 

 to 8 feet long ; they lie along the ground, and year by year, though 

 torn into shreds, they keep their vitality. The portion of the stem 

 above these two leaves "has the appearance of a 2-lobed depressed 

 mass ; it is sometimes 14 feet in circumference, and looks like a round 

 table." The flowers spring from the rim of this table. They are 



