162 



K'NOWLEDGE 



[July 1, 1899. 



It is curious thus to see these similar forms assumed by 

 the mighty trees and by their poor little and very distant 

 relatives the myxies ; and yet, perhaps, this similarity is 

 not a mere accident, but the same physiological necessity 

 has in each case produced the same result. In order that 

 the leaves and flowers and fruit may be exposed to the 

 greatest amount of sun and air, and that the fruit may be 

 spread far and wide, it must be supposed that the tree-hke 

 form has been assumed. A globe suggests itself as the 

 most natural form in which a solid mass can obtam an 

 extensive exposure tojthe action of the sun and of the 



Fig. 14. — Pedicels aad Capillitia of Comalricha oltusata. 



atmosphere if they operated equally all round. We say 

 the most natural, as it would result from an equal and 

 universal outward growth, but for the purpose of exposing 

 its surface, the globe must be mounted on a stand ; but as 

 the lower part will be of less value than the top and sides, 

 because less exposed to the action of the sun, it will be 

 convenient that the globe form shall be modified ; and this 

 has been sometimes attained by horizontal, sometimes by 

 vertical expansion. Some such physical necessities seem 

 to have influenced the shape of trees ; and similar ends 

 are, we suppose, subserved by the dendroid forms of the 

 capillitium in Comatrklw and Stemonitis. How has the 

 chasm between the need and the supply been filled up in 

 these minute organisms or in the stately oak '? 



Another fact which creates further varieties in the form 

 of the sporangia is the presence of lime in the capillitium 

 and in the coats of the sporangium. In this presence of 

 the carbonate of calcium in the sporangium, a character 

 has been found for one of the subdivisions of the myxies, 

 the so-called Cakarinea. In some cases the lime is found 

 in small grains in the substance of the covering membrane, 

 in other cases it is found in star-shaped crystals lying on 

 the outside of the membrane. These are very beautiful 

 objects, and may both be seen in the genus Duiymium. 



In some cases the walls of the sporangium alone have 

 the lime and the capillitium is without it ; in many other 

 cases the lime is found also on the capillitium, and that in 

 different forms. We have already in our sketch of the life- 



history of Badhamia utricularis described the delicate lime 

 structure of its sporangium. 



Amongst all the dehcate forms of the myxies there is 

 none perhaps more beautiful than that of the genus 

 Craterium. The sporangium, as the name of the genus is 

 meant to tell, is goblet-shaped, and the top of the cup is 

 usually covered with a distinct lid, which rests on the sides 

 of the cup. In C. pedunculatum the colours sometimes 

 suggest the notion of a golden cup with a silver lid, and 

 in this dainty cup is found a capillitium of large white 

 lime knots, connected by delicate hyaline or yellow threads, 

 as shown in some of the broken sporangia of Fig. 8. 



It has been suggested that the lime is to be regarded 

 merely as an excretion, a thing of which the organism 

 desires to be rid in its actively living parts. Be it so or 

 not, it is evident that the organism sometimes continues 

 to make this substance subserve the useful purpose of 

 support. 



It is worth while to note the several ways in which the 

 capillitium appears to be used to attain the same end — the 

 maturing and disposal of the spores. Sometimes it is the 

 untwisting of the hygrometric spiral hairs which disperses 

 them (as in Trichin, Fig. 12) ; sometimes it is the uprising 

 of the elastic pillow contained in the sporangium (as in 

 Arci/rifi, Fig. 6) ; sometimes it is by the spreading branches 

 of the capillitium that the spores are scattered over a wide 

 surface, as in Enerthenema : sometimes they are inelastic 

 and charged with lime, and are then used as beams to 

 prevent the walls of the sporangium from falling in and so 

 injuring the young spores (as in Badhamia, Fig. 2). This 

 wealth of plan, this variety of scheme for effecting the 

 same end, and with the same or nearly the same materials, 

 is not unfrequently found in the works of Nature. One 

 might suppose, if Nature were striving to do the one thing 

 needful with the utmost economy, and in the very best 

 way, that there would be one, and only one way which was 

 the cheapest and best, and that this would, on the principle 

 of the survival of the fittest, be found everywhere to pre- 

 vail. But this is by no means always the case. Look at 

 the vast variety of schemes by which, in orchids, insects 

 are made to solve the problem of getting the pollen-masses 

 out of the boxes into which they have been stowed away, 

 and then of pollinating with them the stigmatic surface. 

 Or look again at the vast variety of the forms of the peri- 

 stomes in mosses (all varieties of the same elements and of 

 the same fundamental idea), and the various ways in 

 which they operate under the action of moisture. Or take 

 again the insectivorous plants. Here the problem which 

 Nature seems to have set herself is this — given a leaf, how 

 to catch insects ? And this problem has been solved by 

 the use of different constituent parts of a leaf in almost as 

 many ways as there are genera of insectivorous plants. 

 Or, once more, take the case of birds fitted for subaqueous 

 locomotion. Here the problem seems to have been — given 

 wings and legs, how to drive the body through the water ? 

 and this has been solved, as we know, sometimes by using 

 the wings, sometimes the feet, as paddles, and with a 

 wealth of variation that is very remarkable. In all these 

 cases Nature seems not to ask herself what is the single 

 best way of using the instruments at command, but, given 

 certain organs, how to attain the end in view with the 

 greatest amount of variation ! 



The Opening of the Sporangia. — In some cases, as 

 already mentioned, the sporangium opens by an indetermi- 

 nate rupture, in other cases Nature differentiates it into 

 two parts, the upper forming sometimes a lid, as in 

 Craterium, sometimes falling away early, as in Arcyria. 

 Just the same kind of difference prevails, it will be 

 remembered, in the mosses, the sporangia of the clay 



