766 BOTANY. 
fertilizing themselves, and at the same time to attract insects to do 
it for them. Dr. Engelmann had this year discovered that Yucca 
was one of those plants which depended on insects for fructifica- 
tion, and Prof. Riley had discovered that the little moth in ques- 
tion, which he calls Pronuba yuccasella, is the only insect which 
can have anything to do with this fructification. But what is more 
interesting in this case is, that the plant not only depends on the 
assistance of the moth, but that the moth, in turn, is likewise 
- dependent upon the plant, since its larvae live on the seeds. We 
have, consequently, a mutual interdependence which is very strik- 
ing, and in the structure of the female moth there is a curious 
adaptation of means to an end by a complete modification of 
parts, and especially of the maxillary palpi, which are formed into 
prehensile tentacles, by which she collects the pollen to insert it 
into the stigmatic tube. 
Trees and Rain.— The influence of trees upon rains and the 
general moisture of the atmosphere, which has ‘been so much 
discussed of late, receives a strong illustration from the island of 
Santa Cruz, W. I. 
A friend who spent the months of February, March and April 
last upon the island informs me that when he was there twenty 
years ago, it was a garden of freshness, beauty and fertility. 
Woods covered the hills, trees were everywhere abundant and 
rains were profuse and frequent. The memory of its loveliness 
called him there at the beginning of the present year when, ss 
‘his astonishment, he found about one-third of the island, which is 
about twenty-five miles long, an utter desert. The forests and 
trees generally had .been cut away, rainfalls had ceased and a 
process of desiccation beginning at one end of the island had 
advanced gradually and irresistibly upon the island, until for 
seven miles it is dried and desolate as the sea-shore. Houses and 
beautiful plantations have been abandoned, and the people watch 
the advance of desolation, unable to arrest it, but knowing almost 
to a certainty, the time when their own habitations, their gardens 
and fresh fields will become a part of the waste; the whole island 
~ seems doomed to become a desert. oo 
_ The inhabitants believe, and my friend confirms their opimon:, 
that this sad result is due to the destruction of the trees upon the — 
island some years ago.— J. S. M. - 
