OF FILAMENTOUS, FRUTICULOSE, AND FOLIACEOUS LICHENS. 117 
among the spermatiferous sterigmata, which they greatly exceed, both in length 
and tenuity. Their extremities are usually more or less knobbed or bulging. 
b. Spermatia are solid bodies, colourless and transparent; homogeneous, 
having no contents and showing no septa; generally more or less linear in form, 
and of equal thickness throughout; never quite spherical; of extreme tenuity; 
exhibiting great uniformity in size and shape; devoid of cilia or other ap- 
pendages ; possessing Brownian or molecular movements in water; having no 
power of germination; never intermixed with oil globules, but imbedded ina 
mucilage. 
These essential characters it is of importance to bear in mind, especially in 
contrasting, as to function, spermatia with stylospores. 
Form a. Straight.—1. Rods with obtuse ends, or needles with pointed ends, 
in all species with arthrosterigmata. This, therefore, is the commonest 
form of spermatium. 
2. Oblong, oval-oblong or ellipsoid in Ramalina, Lichina, and Ephebe. 
b. Curved.—1. Shortish ; sickle-shaped or crescentic ; of equal thickness 
throughout, and with blunt ends, or thickest in the centre ; with pointed 
ends in Cladonia, Roccella, Stereocaulon. 
2. Long; twisted or vermiform in Squamaria. 
Size.—The length of the spermatia varies from ath to eoth of an inch, a 
medium or average being 3th to ;;th. Sometimes, though rarely, asin Parmelia 
tiliacea occasionally, they are twice as long when attached as when free. But, in 
such cases, it would appear that, when thrown off from the sterigmata, they divide 
into two equal segments. Their breadth is most frequently about month to sonth, or 
it is so small as scarcely to admit of measurement. The following micrometrical 
scale, applied to the /ength of the spermatia, may assist the reader :— 
1. Very minute, ; ; . . . ae inch to a0 
re eenute, : 2 : . : 3 ae eile 8000 
3. Smallish, . : . ; : a0 see sam 
4. Medium size, ; ; - : : oe codes bear, 
5. Longish, . : . ° : . ima (eae 
6. Verylong, . : y - . : aan a 
Position on the Sterigmata.—They are given off from— 
a. Apices only, in simple sterigmata. 
b. Apices and sides, in compound or articulated ones. 
Development.—The spermatium first appears as a minute, papillar bulging of 
the apex of the sterigmatic filament or cell. This papilla gradually becomes 
elongated, and when maturity has been arrived at, a line of separation becomes 
marked, and the spermatium falls from its parent cell and base of support. Each 
VOL. XXII. PART I. 2H 
